360=x+100+120+100 I'm not sure what __=360

Which values for a and b will create infinitely many solutions for this system of equations? ax-y=8 2x+y=b

Prove that the value of the expression 7^8–7^7+7^6 is divisible by 43.

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?