7x + 5 = 3x - 15
solve for x

7x+5=3x-15 x=-5

Step-by-step explanation:

Subtract from both sides

7x+5-5=3x-15-5

{Simplify}

7x=3x-20

{Subtract}{3x from both sides}

7x-3x=3x-20-3x

{Simplify}

4x=-20

Divide both sides by 4

4x over 4= -20 over 4

 {Simplify}  

  x=-5

circle area = pi * radius^2

if diameter = 10 then radius = 5

circle area = pi * 5^2

circle area = pi * 25

circle area = 78.5398163397 square units

step-by-step explanation: