use substitutio method

y+x=7
3x+y=15

3 answers

y+x=7
3x+y=15

y = 7 - x

3x + 7 - x = 15

2x = 8

x = 4

Take it from there.
a bucket is 44cm in diameter at the top and 24cm at diameter at the bottom.Find its capacity in litres if its 36cm deep
y+4=7
y=3
(3×4)+y=15
12+y=15
y=3
answer=....x=4 and y=3