24x-1.6x=36
365+199= 40÷90= 0.8÷10%= 5.98+0.2= 2.5×400=
- = ÷ = 1÷ = + = × ÷ × =
①75%x=360
②(1-55%)x=90
③31%x-66=8.4
④25%x+50%x=420