Abox have 108 colored pencils 1/3 are blue 5/12 are green 1/10 are red and the rest are yellow what is the fraction and how many yellow pencils are there

1) prove that 731^3−631^3 is divisible by 100 2) prove that 99^3−74^3 is divisible by 25

I’m really confused and need your assist me with this question i’ve never been taught

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! )