philip is 4 less than 3 times kevins age. kevins age is twice as much as colbys age. the sum of their ages is 131 years old. how old is colby?
i found the answer!
6x-4 2x x
[-------------------]---------------------------]---------------]
philip kevin colby

6x-4 9x-4=131
2x +4= +4
x ----------------
---- 9x = 135
9x-4=131 /9 = /9
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x = 15