Answer number 3 in the picture pls! I really need the help

Prove that the sum of two consecutive exponents of the number 5 is divisible by 30.if two consecutive exponents are 5n and 5n + 1, then their sum can be written as 30.

Aquantity with an initial value of 3900 decays exponentially at a rate of 35% every hour. what is the value of the quantity after 0.5 days, to the nearest hundredth?

At your job you're paid $50 per week plus $3 per sale at least how many saled do you need to make in order to have over $250