What is the area of triangle JKL?

Twice the sum of a number and 4 is equal to three times the difference of the number and 7. find the number.

Find the midpoint m of z1=(8+5i) and z2=(12+3i)

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?