(t²+8t-9)-(t²-11t+10)=18t-20
t²+8t-9-t²+11t-10=18t-20
19t-19=18t-20
19t-18t=19-20
t=-1
1)t^2 + 8t - 9 -t^2 + 11t - 10=18t-20
2)19t-19 = 18t -20
3)19t-18t= -20 +19
4)1t= -1
5)t= -1/1 = -1
