7*(x - 7) = 126 <=>
x - 7 = 18 <=>
x = 25
Each hour,
x makes b/6 bearings
y makes b/4 bearings
z makes b/3 bearings
Together, each hour, x, y and z together make
b/6+b/4+b/3=b(1/6+1/4+1/3)=b(2/12+3/12+4/12)=b(3/4)=3b/4 bearings.
Time to make b bearings =
b/(3b/4)=4/3 hours = 1 hour 20 minutes.
The correct answer for USATesprep is
C) 3 cm, 4 cm, 5 cm
