Chapter 7 - Section 7.6 - Proportions and Problem Solving with Rational Equations - Exercise Set - Page 541: 64

24/5 hours

Smith balances in 8 hours (1/8 done in an hour) assistant balances in 12 hours (1/12 done in an hour) $1/8 + 1/12 = 1/x$ $48(1/8 + 1/12 = 1/x)$ $6 + 4 = 48/x$ $10 = 48/x$ $10*x=48/x*x$ $10x=48$ $10x/10 = 48/10$ $x = 48/10$ $x= 24/5$