Question

Please help I don't understand 120 - 28a = 78

Answer 1

Simplifying
120 + -28a = 78

Solving
120 + -28a = 78

Solving for variable 'a'.

Move all terms containing a to the left, all other terms to the right.

Add '-120' to each side of the equation.
120 + -120 + -28a = 78 + -120

Combine like terms: 120 + -120 = 0
0 + -28a = 78 + -120
-28a = 78 + -120

Combine like terms: 78 + -120 = -42
-28a = -42

Divide each side by '-28'.
a = 1.5

Simplifying
a = 1.5

Answer 2

120 - 28a = 78
28a = 120-78
28a = 42
$a = \frac{42}{28} \\ a = \frac{3}{2}$