Question 1173746
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With formal algebra....<br>
m = Minah's age
m+4 = Corrine's age (4 years older than Minah)
m-1 = Minah's age last year
m+3 = Corrine's age last year<br>
The sum of their ages last year was 28:<br>
{{{(m-1)+(m+3) = 28}}}<br>
Solve using basic algebra.<br>
Solving informally can give you some good practice with logical reasoning and mental arithmetic:<br>
Last year the sum of their ages was 28, so this year that sum is 30.
Now separate 30 into two ages that differ by 4.  One way to do this easily mentally is to see that two identical ages 15 and 15 add to 30; to get two ages that differ by 4 you can add 2 to one of them and subtract 2 from the other to get the answers of 13 and 17.<br>