#### Answer

The solution of this equation is x = 200

#### Work Step by Step

0.07x + 0.08(x + 600) = 78
Use the distributive property to obtain:
0.07x + 0.08x + 48 = 78
In order to solve for x, we first need to get all of the terms with an x in them on the same side of the equation:
Thus, we obtain:
0.07x + 0.08x = 78 - 48
0.07x + 0.08x = 30
0.15x = 30
Divide both sides by 0.15:
x = 200
The solution of this equation is x = 200