Let x represent the cost of book B
Book A: $17.50
Book B: x
Sales tax: (A + B) x 6% = .06(17.50 + x) = 1.05 + .06x
book A + book B + sales tax = total cost
(17.50) + (x) + (1.05 + .06x) = 44.52 plugged in all of the values
18.55 + 1.06x = 44.52 added like terms
1.06x = 25.97 subtracted 18.55 from both sides
x = 24.50 divided 1.06 from both sides
Answer: $24.50