1.
x÷0.8=6×1.6
x=6×1.6×0.8
x=7.68
2.
45÷x=2.5×2
45÷2.5÷2=x
x=9
3.
3.6x-x=1.3×4
(3.6-1)x=5.2
x=5.2÷2.6
x=2