应该是x=42+5+7x=47+7x=54
10.5×8/2=120/2=60
x-7-5=42解x-7=42+5 x-7=47 x=47+7 x=54
×-7-5=42×-7-5+7+5=42+7+5×=49+5×=54
X-7-5=42解： X=42+7+5 X=54
