13. D
12000000+100000x=20000000+80000x
100000x-80000x=20000000-12000000
20000x=8000000
x=400
12000000+100000(400)=20000000+80000(400)
52millones=52millones
14.C
12000000+100000(100)=20000000+80000(100)
22millones=28millones
22millones=75.57142857%
28millones=100%
100%-75.57142857%=21.42857143%
15.A
12000000+100000(401)=20000000+80000(401)
52100000=52080000
16.A
6+1/5x=x
0.8x=6
x=7.5kg