Appendix A - A.2 - Formulas and Equations - Exercises - Page 546: 32

n=12

We can multiply by n assuming that n≠0 because it's the denominator of a fraction: $(n-2)\times 180 = 150n$ By expanding the brackets we have: $180n -2\times 180 = 150n$ $180n -360 = 150n$ We can add 360 to and subtract 150n from both sides: $180n-150n= 360$ $30n=360$ We can divide by 30: $n=12$