Need help ASAP have a timed quiz and I don't understand the last question

Plzzz maths ! quadratic sequences=an^2+c 1) 11,17,27,41,59 2) 7,16,31,52,79 3) 6,18,38,66,102 4) 0,9,24,45,72 5) 0,12,32,60,96

Angles r and s are complementary. the measure of angle r is 31 degrees. which equation can be used to find angle s?

How are algebraic expressions evaluated using substitution?