Question 175513
Let the brothers be {{{x}}} years old.  Then Mary is {{{x + 3}}} years old.  Next year the brothers will each be {{{x + 1}}} and Mary will be {{{x + 4}}}.  We are given that {{{(x + 4) + (x + 1) + (x + 1) = 102}}}.


Remove parentheses and collect terms:


{{{3x + 6 = 102}}}


{{{3x = 102 - 6 = 96}}}


{{{x = 96/3 = 32}}}.


So the brothers are 32 now and Mary is 35 now.


Check:  33 + 33 + 36 = 102.