What's S? Please show steps, Thank you!

Question

9t+16s=1062

t+s=90

Answer 1

t + s = 90                       subtract s from both sides

t = 90 - s                        substitute in first equation

9(90 - s) + 16s = 1062   distribute

810 - 9s + 16s = 1062 combine

810 - 7s = 1062           subtract 810 from both sides

-7s = 252                     divide both sides by -7

s = -36