notice that the angles of the right triangle are 40 and 50 degrees, with the 500 meter side adjacent to the 50 degree angle. now, we can set up an equation: cos (50 degrees) = 500 / x. use a calculator to find that the answer is 777.9.
25 and -31
notice that if all the negatives were positive, you would have the arithmetic sequence 1, 7, 13, 19, on and on, adding 6 every time. so basically we have a geometric and arithmetic sequence combined, with the geometric sequence making it positive, and negative, and the arithmetic sequence adding 6 every time. this means the answer(s) are 25 and -31.
19.75 / 5 * 9