解:28-X+3.1=15
x=28+3.1-15
x=16.1
28-X+3.1=15
① 将3.1移到右边:28-X=15-3.1
② 将-X移到右边:28=15-3.1+X
③ 将15移到左边:28-15=3.1+X
④ 将3.1移到左边:28-15-3.1=X
⑤ 将28移到右边:X=28-15-3.1
答案:X=9.9
28-X+3.1=15怎么解?
解:
28-x+3.1=15
31.1-x=15
x=31.1-15
x=16.1
31.1-x=15
x=31.1-15
x=16.1