What times what equals 88 and added equals 18?

Let the number be 'm' & 'n'

Hence mn = 88

m + n = 18

m = 18 - n

Substitute

(18 - n)n = 88

18n - n^2 = 88

n^2 - 18n + 88 = 0

This does not readily factor so apply the Quadratic Eq'n.

n = { --18 +/-sqrt[(-18)^2- 4(1)(88)]} 2(1)

n = { 18 +/- sqrt[324 -352]} / 2

n = { 18 +/-sqrt[-28]} / 2

This is unresolved as you cannot take the 'square root; of a negative number.