exam Maths Puzzle Numerical Ability

21-[-(3-4)-2]-5
21-[-3+(-4)-2]-5
21-[-7)-2]-5
21-[-7+(-2)-5
21-(-9)-5
21+9-5
30-5
25

Textbook gives this answer as 17

What am I doing wrong?

Thank you.

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exam Other Question

Factor completely.

2x squared + 7x - 4
Using synthetic division, determine whether the numbers are zeros of the polynomial.
5, 0; f(x)=2x^4-8x^3-15x^2+30x-25