The number of cakes that Brad made = 19 cakes
We are given;
Total number of cakes made by Brad and Sally = 31
Let the number of cakes made by Brad be x.
Thus;
Number of cakes made by Sally = x - 7
x + x - 7 = 31
2x - 7 = 31
2x = 31 + 7
2x = 38
x = 38/2
x = 19
Thus,
Number of cakes made by Brad = 19
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