x/3+y/4=54/60(1)
x/5+y/4=42/60(2)
(4x+3y)/12=54/60 (3)
(4x+5y)/20=42/60 (4)
(4x+3y)=54/5 (5)
(4x+5y)=42/3 (6)
5*(4x+3y)=54 (7)
3*(4x+5y)=42 (8)
20x+15y=54 (9)
12x+15y=42 (10)
8x=12
x=1.5
15y=54-30=24
y=1.6