Devin has 39 toy blocks. what is the value of the digit 9 in this number

Which shows the correct solution of the equation 1/2a+2/3b=50, when b=30?

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?

Factor the polynomial expression x6 – x3 – 20