Question 121345
x+y=90 or x=90-y
12x+16(90-x)=1350
12x+1440-16x=1350
-4x=1350-1440
-4x=-90
x=-90/-4
x=22.5 hours for the bricklayer.
90-22.5=67.5 hours for the electrician.
proof
12*22.5+16*67.5=1350
270+1080=1350
1350=1350