Answer
$x = 50$
Work Step by Step
Multiply $100$ to both sides of the equation to obtain:
$100[0.08x+0.06(x+12)]=100(7.72)$
Distribute $100$ to obtain:
$100(0.08x) + 100[0.06(x+12)]=772
\\8x+6(x+12)=772$
Distribute $6$, then combine like terms to obtain:
$8x+6(x) + 6(12) = 772
\\8x+6x+72=772
\\14x+72=772$
Subtract $72$ to both sides of the equation:
$14x=700$
Divide $14$ to both sides of the equation:
$\dfrac{14x}{14} = \dfrac{700}{14}
\\x = 50$
