Question 1108753
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The algebraic solution outlined by the other tutor is certainly valid; you should know how to solve problems like this using that method.<br>
But it is also good to be able to understand what is happening in the problem so you can see how to get the solution informally, by logical reasoning.<br>
For this type of problem, where you are given the sum and difference of two numbers, think of a number line.  You start at one of the two numbers; to get the sum of the two numbers, you go one direction on the number line from the first number; to get the difference, you go the opposite direction.<br>
That means the first number is halfway between the sum and difference of the two numbers -- i.e., it is the average of the sum and difference.<br>
So in this example, a quick way to the solution is to see one number as {{{(61+13)/2 = 74/2 = 37}}}; then the other number must be 24.