Verified Answer :

11.p=-8, 17-8=9
12.y=11, 311=33+16=46
13.t=4, 4
4=16-14=2
14.x=9, -9x 98=82-9=72-9=62
15.z=4, 12
4=48-18=30
16.g=0, 40=0, 7+0=7
17.x=4, 9
4=36-24=-3
18.q=3, 183=48+2=50
19.c=2, 3
2=6-4.5=4.1
20.y=4, 9+4=13+4.8=17.4