①17+6x=149
②
③0.4x+3.5x=6.24
④x:5=18:15
5%×10= 200×80%= 20÷20%= 1﹣75%= 2+150%=
15÷30%= 15×30%= 42÷60%= 90×4.5%= 16÷50%=
①6.4×2.5×1.25
②8.5×98%
③÷4+×
④×