PLZ help answer these i´ll mark the brainlest if u answer them all and explain

Including 6% sales tax, an inn charges $135.68 per night. find the inns nightly cost

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?

Ineed to know the ordered pairs for this equation i need the answer quick because it’s a timed test