Question

Robin has triple as many marbles Amy. Sam has 15 more marbles than robin. Together they all have 99 marbles. How many marbles does each person have

Answer 1

Let: x be Amy's marbles
3x be Robin's marbles
15+3x be Sam's marbles
x+3x+15+3x=99
7x+15=99
7x=99-15 (transfer 15 to the right side of the equation, then minus)
7x/7=84/7 (divide both sides of the equation by 7)
x=12
Now substitute:
x = 12 (Amy's)
3x = 3*12 = 36 (Robin's)
15+3x = 15+3*12 = 51 (Sam's)
12+36+51 = 99
Therefore, Amy has 12 marbles, Robin has 36 marbles and Sam has 51 marbles.