L=2J Leo had twice as many as John
let j = how many J gave away
L-3j = 15 Leo gave away 3 times as many as John gave away and had 15 left
substitute 2J or L
2J -3j =15
J-j = j-10 after he gave j away, John had 10 less than he gave away
J-2j =-10
2J-4j =-20 subtract from the last equation ending in =15 to eliminate J
j =35
J-2(35)=-10
J=60 originally
L=120 originally