Robert and Steven had some pens in the ratio of 3:2. After Steven gave 8 pens to Robert, the ratio of the number of pens Robert had to the number Steven had became 13:2. How many pens did Robert have at first?
Let pens with Robert be 3x and pens with Steven be 2x
After Steven gave 8 pens to Robert, pens with Robert = 3x+8 and pens with Steven= 2x-8 and the ratio =13:2
3x+8/2x-8=13/2
cross multiplication
2(3x+8)=13(2x-8)
6x+16=26x-104
26x-6x=16+104
20x=120
x=120/20=6
Number of pens with Robert at first=3*6=18
