One number is one-fifth of another number. The two numbers total 18. Find the numbers

One number is 17 and the other is 85.

Step-by-step explanation:

Let the numbers be m and n. Let m = (1/5) n. Note that m+n = 18.

Substituting (1/5) n for m in the 2nd equation, we get (1/5) n + (5/5) n = 18. Multiplying all three terms by 5 to remove fractions, we get n + 5 = 90, so that n = 85. m is (1/5) of 85, or m = 17.