Can someone help me with this?

16 18 If ( > 0 and t2 - 4 = 0, what is the value of f ? x+ y=-9 x + 2y= -25 According to the system of equations above, what is the value of x ? 17 19 In a right triangle, one angle measures x", where x feet sin x* = =. What is cos(90' - x") ? E C 20 A summer camp counselor wants to find a length, x. If a = 5v2 and 2a = v2x, what is the value of x ? in feet, across a lake as represented in the sketch above. The lengths represented by AB, EB, BD, and CD on the sketch were determined to be 1800 feet, 1400 feet, 700 feet, and 800 feet, respectively. Segments AC and DE intersect at B, and ZAEB and ZCDB have the same measure. What is the value of x