Divide both sides by $\displaystyle -5$:

$\displaystyle -5x = -70$

$\displaystyle -5x \div (-5) = -70 \div (-5)$

$\displaystyle x = -70 \div (-5) = + (70\div 5) = 14$

Add 28 to both sides:

$\displaystyle x - 28 = 82$

$\displaystyle x - 28 + 28 = 82 + 28$

$\displaystyle x = 110$

$\displaystyle 3x - 9= 30$

$\displaystyle 3x - 9 + 9= 30+ 9$

$\displaystyle 3x = 39$

$\displaystyle 3x \div 3 = 39 \div 3$

$\displaystyle x = 13$

$\displaystyle 3x + 9= 30$

$\displaystyle 3x + 9 - 9= 30- 9$

$\displaystyle 3x = 21$

$\displaystyle 3x \div 3 = 21 \div 3$

$\displaystyle x = 7$

The measure of $\displaystyle \angle2$ is twenty degrees greater than the measure $\displaystyle x$ of $\displaystyle \angle 1$, so its measure is 20 added to that of $\displaystyle \angle 1$ - that is, $\displaystyle x + 2 0$.

The measure of $\displaystyle \angle 3$ is thirty degrees less than twice that of $\displaystyle \angle 1$. Twice the measure of $\displaystyle \angle 1$ is $\displaystyle 2x$, and thirty degrees less than this is 30 subtracted from $\displaystyle 2x$ - that is, $\displaystyle 2x-30$.

The sum of the measures of the three angles of a triangle is 180, so, to solve for $\displaystyle x$ - thereby allowing us to calulate all three angle measures - we add these three expressions and set the sum equal to 180. This yields the equation:

$\displaystyle x + (x+20) + (2x-30) = 180$

The measure of $\displaystyle \angle2$ is forty degrees less than the measure $\displaystyle x$ of $\displaystyle \angle 1$, so its measure is 40 subtracted from that of $\displaystyle \angle 1$ - that is, $\displaystyle x -40$.

The measure of $\displaystyle \angle 3$ is ten degrees less than twice that of $\displaystyle \angle 1$. Twice the measure of $\displaystyle \angle 1$ is $\displaystyle 2x$, and ten degrees less than this is 10 subtracted from $\displaystyle 2x$ - that is, $\displaystyle 2x-10$.

The sum of the measures of the three angles of a triangle is 180, so, to solve for $\displaystyle x$ - thereby allowing us to calulate all three angle measures - we add these three expressions and set the sum equal to 180. This yields the equation:

$\displaystyle x + (x-40) + (2x - 10) = 180$

$\displaystyle -5 (x-12) = -35$

$\displaystyle -5 \cdot x- \left (-5 \right ) \cdot 12 = -35$

$\displaystyle -5x- \left (-60 \right ) = -35$

$\displaystyle -5x+60= -35$

$\displaystyle -5x+60 -60= -35-60$

$\displaystyle -5x= -95$

$\displaystyle -5x \div (-5)= -95\div (-5)$

$\displaystyle x=19$

$\displaystyle 5x + 15 = x + 84$

$\displaystyle 5x -x+ 15 = x-x + 84$

$\displaystyle 4x+ 15 = 84$

$\displaystyle 4x+ 15-15 = 84-15$

$\displaystyle 4x = 69$

$\displaystyle 4x \div 4= 69\div 4$

$\displaystyle x = 17\frac{1}{4}$

$\displaystyle 3x -21=66$

$\displaystyle 3x -21+ 21=66+ 21$

$\displaystyle 3x =87$

$\displaystyle 3x\div 3=87\div 3$

$\displaystyle x=29$

$\displaystyle 4x - 15 = x + 84$

$\displaystyle 4x-x - 15 = x -x+ 84$

$\displaystyle 3x - 15 = 84$

$\displaystyle 3x - 15 +15= 84+15$

$\displaystyle 3x = 99$

$\displaystyle 3x \div 3 = 99\div 3$

$\displaystyle x=33$