2X+2.8=6.5
2X=3.7
X=1.85.
12.5X=3/8,
X=3/8×2/25
X=3/100,
题目不全.
8.3-7X=3.4
7X=4.9
X=0.7
6X=4/5×3/4
6X=3/5
X=1/10