How many digits can be formed using the numbers 3,4,5,6,7,8,9 if they can be repeated

Pat listed all the numbers that have 15 as a multiple write the numbers in pats list

Another type of subtraction equation is 16-b=7. explain how you would sole this equation then solve it.

You are standing next to a really big circular lake. you want to measure the diameter of the lake, but you don't want to have to swim across with a measuring tape! you decide to walk around the perimeter of the lake and measure its circumference, and find that it's 400\pi\text{ m}400? m. what is the diameter dd of the lake?