If the gradient of a line, C, is 2/3, what is the gradient of a line which perpendicular to C

Need this at the city museum, child admission is 6 and adult admission is 9.20. on tuesday, 132 tickets were sold for a total sales of 961.60. how many adult tickets were sold that day?

The angle of elevation from point a to the top of the cliff is 38 degrees. if point a is 80 feet from the base of the cliff , how high is the cliff ?

Find the sum of the given arithmetic series. 24 + 17 + 10 + 3 + + (–39)