Question 235944
Write an equation for each statement, rewrite the equations to get it in terms of A
:
A is 9 years younger than B,
A = B-9
B = A+9
:
and 6 years older than C;
A = C+6
C = A-6
:
 three fourth's of A's age, four fifth's of B's and one half of C's amount to 37 years. 
.75A + .8B + .5c = 37
:
Replace B & C from the 1st two equations
.75A + .8(A+9) + .5(A-6) = 37
:
.75A + .8A + 7.2 + .5A - 3 = 37
:
.75A + .8A + .5A + 7.2 - 3 = 37
:
2.05A + 4.2 = 37
:
2.05A = 37 - 4.2
:
2.05A = 32.8
A = {{{32.8/2.05}}}
A = 16 yrs old
;
I'll let you find the ages of B & C, check your solutions in the last equation