What number must you add to the expression below to complete the square? x^2-20x?

Find the value of tan theta if sin theta = 12/13 and theta is in quadrant 2

The swimming pool is open when the high temperature is higher than 20∘c. lainey tried to swim on monday and thursday (which was 3 days later). the pool was open on monday, but it was closed on thursday. the high temperature was 30∘c on monday, but decreased at a constant rate in the next 3 days. write an inequality to determine the rate of temperature decrease in degrees celsius per day, d, from monday to thursday.

I'm confused on this could anyone me and show me what i need to do to solve it.