Final answer:
To find the number of letters received, we set up an equation using the given information and solve for the variable representing the number of letters.
Step-by-step explanation:
To solve this problem, let's set up an equation. Let L represent the number of letters, M represents the number of magazines, B represents the number of bills, and A represents the number of ads. We know that L = M and B = M + 3. We also know that A = B + 5. We can translate the given information into equations:
L + M + B + A = 15
L = M
B = M + 3
A = B + 5
Substituting the values of L, B, and A into the first equation:
M + M + (M + 3) + (M + 3 + 5) = 15
Combining like terms:
4M + 11 = 15
Subtracting 11 from both sides:
4M = 4
Dividing both sides by 4:
M = 1
Since L = M, we know that L = 1. Therefore, the Brady family received 1 letter.