let

x = the number of marbles sara has

y = the number of marbles alia has

z = the number of marbles ambreen has

sara,aliya,and ambreen share 480 marbles:

x + y + z = 480

aliya has twice as many marbles as sara

y = 2x

ambreen has three times as many marbles as sara:

z = 3x

by solving the system of equations:

x + y + z = 480

y = 2x

z = 3x

we find:

x = 80 marbles

y = 160 marbles

z = 240 marbles

click here to see the step by step solution of the system of equations:

Sara has 80 marbles.