Question 431697
Mark is 4 years older than Kate.
m = k+4 
:
Together the sum of their ages is three times Kate's age.
m + k = 3k
Replace m with (k+4)
k + 4 + k = 3k
2k + 4 = 3k
4 = 3k - 2k
4 = k
:
How old are each? Mark is 8, Kate is 4