To solve this problem, we must set up a system of equations. In this case, let's let Maggie's age be represented by the variable m and her brother's age be represented by the variable b. We are told that the sum of their ages is 24, which gives us our first equation: m + b = 24. We can construct our next equation from the first sentence of given information: b = 2m - 3. This makes our system of equations:
m + b = 24
b = 2m - 3
To solve, we are going to substitute the value for b in terms of m given by the second equation into the first equation for the variable b.
m + b = 24
m + 2m - 3 = 24
To simplify, we must first combine the variable terms on the left side of the equation using addition.
3m - 3 = 24
Next, we should add 3 to both sides of the equation to get the variable term alone on the left side of the equation.
3m = 27
Finally, we should divide both sides by 3 in order to get the variable m alone.
m = 9
Therefore, Maggie is 9 years old (using the first equation and substituting in this value you can find that her brother is 15 years old).
Hope this helps!