Question

A student ate 3/20 of all candies and another 1.2 lb. Another student ate 3/5 of the candies and the remaining 0.3 lb. Altogether, what weight of candies did they eat?

Answer 1

let
x-------> total weight of candies
we know that

x=(3/20)*x+1.2+(3/5)*x+0.3
x=(3/20)*x+(3/5)*x+1.5----> multiply by 20----> 20x=3x+12x+30
20x=15x+30
20x-15x=30
5x=30
x=6 lb

the answer is
6 lb