Question 15: Natural number x given by : \(5(x + 15) = 5^3\) . What is the value of x:

\(\begin{array}{*{20}{l}} {5(x + 15) = {5^3}}\\ {5(x + 15) = 125}\\ {x + 15 = 125 :5}\\ {x + 15{\mkern 1mu} = 25}\\ {x{\mkern 1mu} {\mkern 1mu} = 25 – 15}\\ {x{\mkern 1mu} = 10.} \ end{array}\)