Question

Devaughn is 13 years younger than Sydney. The sum of their ages is77 What is Sydney's age?

Answer 1

s is sydney's age. devaughn's age is d. d=s-13. The total sum is 77=s+d OR 77=s+s-13. 77=2s-13. add 13 to both sides. 90=2s. sydney's age is 45. to check, substitute sydney's age in. d=45-13=32. 77=45+32=77.

Answer 2

77=x+x-13
77=2x-13
-2x=-13-77
-2x=-90
x=45
Sydney's age is 45