2.1X+7.9X=6.9
10x=6.9
x=0.69
5X+0.8×2=7.3
5x+1.6=7.3
5x=5.7
x=1.14
12X+5.8=8.2
12x=2.4
x=0.2
6X-3×4=1.2
6x-12=1.2
6x=13.2
x=2.2
2.1X+7.9X=6.9
10x=6.9
x=0.69
5X+0.8×2=7.3
5x+1.6=7.3
5x=5.7
x=1.14
12X+5.8=8.2
12x=2.4
x=0.2
6X-3×4=1.2
6x-12=1.2
6x=13.2
x=2.2