I don’t know the answer I’m not that smart help

Thank you

4+(2+x) can you me solve this problem

Prove that 16^4-2^13-4^5 is divisible by 11.

I'm at a bookstore with $\$35$ in my pocket and a $20\%$-off coupon. what is the cost of the most expensive book i can buy with my money and the coupon? (assume that there are books of every possible price in the bookstore. it's a large bookstore! )