3x-= x+= +-x=
①2y+y=105 ②6x-25=77 ③
+ = ﹣ = + = 1﹣ ﹣ = + =
﹣ = 1﹣ = + ﹣ = + + + = + ﹣ =
1-= += 12.8-2.8= =
×3= ×= ×0= ×÷×=
0.8+ = 3÷ = + = + = ÷ ×2=
× = ÷ = 6× = - = - × =