SOLUTION: four times mark's age is 4 more than eight times what matt's age was 2 years ago.three times matt's present age is 3 more than what's mark's age was 4 years ago.find thier present

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Question 587649: four times mark's age is 4 more than eight times what matt's age was 2 years ago.three times matt's present age is 3 more than what's mark's age was 4 years ago.find thier present ages.
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +a+ = Mark's age now
Let +b+ = Matt's age now
+a+-+4+ = Mark's age 4 years ago
+b+-+2+ = Matt's age 2 years ago
given:
(1) +4a+=+8%2A%28+b+-+2+%29+%2B+4+
(2) +3b+=+a+-+4+%2B+3+
----------------------
(1) +4a+=+8b+-+16+%2B+4+
(1) +4a+-+8b+=+-12+
and
(2) +a+-+3b+=+4+-+3+
(2) +a+-+3b+=+1+
----------------------
Multiply both sides of (2) by 4
and subtract (1) from (2)
(2) +4a+-+12b+=+4+
(1) +-4a+%2B+8b+=+12+
+-4b+=+16+
+b+=+-4+
I get a negative number which means 4 years
before he was born. Can you find my mistake?
I don't see one.