①42×()
②7.5×(26-10)+9.7
③0.8×4×12.5×2.5
④÷[1-(+0.25) ]
205+97= 3.01﹣0.1= 0.25×3×4= 36×25%=
3×a×a= ×1.6= 4÷25%= 16.4+3.06=
1﹣ ÷ = ( ﹣ )÷ =