



 
Hi Angel, I would solve for Keith's and Alan's present ages and then calculate the ratio. Suppose Keith's current age is $k$ years and Alan's current age is $a$ years. You know that \[k + a = 36.\] How old was Keith 4 years ago? How old was Alan 4 years ago? What was the ratio of their ages 4 years ago? You know this ratio is 4:3 so this gives you a second equation. Write this equation in terms of fractions rather than ratios. You now have two equations on $k$ and $a.$ Solve for $k$ and $a.$ write back if you need more assistance,  


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