Solve for a 3a+15=4(a-5)

$3 a + 15 = 4 (a - 5)$

Step 1

Simplify $4 (a - 5)$ .

Rewrite.

$3 a + 15 = 0 + 0 + 4 (a - 5)$

Simplify by adding zeros.

$3 a + 15 = 4 (a - 5)$

Apply the distributive property.

$3 a + 15 = 4 a + 4 \cdot - 5$

Multiply $4$ by $- 5$ .

$3 a + 15 = 4 a - 20$

Step 2

Move all terms containing $a$ to the left side of the equation.

Subtract $4 a$ from both sides of the equation.

$3 a + 15 - 4 a = - 20$

Subtract $4 a$ from $3 a$ .

$- a + 15 = - 20$

Step 3

Move all terms not containing $a$ to the right side of the equation.

Subtract $15$ from both sides of the equation.

$- a = - 20 - 15$

Subtract $15$ from $- 20$ .

$- a = - 35$

Step 4

Divide each term in $- a = - 35$ by $- 1$ and simplify.

Divide each term in $- a = - 35$ by $- 1$ .

$\frac{- a}{- 1} = \frac{- 35}{- 1}$

Simplify the left side.

Dividing two negative values results in a positive value.

$\frac{a}{1} = \frac{- 35}{- 1}$

Divide $a$ by $1$ .

$a = \frac{- 35}{- 1}$

Simplify the right side.

Divide $- 35$ by $- 1$ .

$a = 35$