Answer:
the positive solution is the number is 9
Explanation:
let the number be n then 7 times the number is 7n and the square of the number is n²
the equation is then
7n = n² - 18 ( subtract 7n from both sides )
0 = n² - 7n - 18 ← quadratic equation in standard form
0 = (n - 9)(n + 2) ← in factored form
equate each factor to zero and solve for n
n - 9 = 0 ⇒ n = 9
n + 2 = 0 ⇒ n = - 2
the positive solution is the number n = 9