Twenty planes are at an airport. Eight planes take off, then five planes land, then 7 more take off, then 9 land. How many planes are left at the airport? PLS HELPP

Factor and solve to find roots x squared -x - 90 =0

Use the following statements to write a compound statement for the conjunction or disjunction. then find its truth value. p: an isosceles triangle has two congruent sides. q: a right angle measures 90° r: four points are always coplanar. s: a decagon has 12 sides. a) a right angle measures 90° or an isosceles triangle has two congruent sides; true. b) a right angle measures 90° and an isosceles triangle has two congruent sides; true. c) a right angle measures 90° and an isosceles triangle does not have two congruent sides; false. d) a right angle measures 90° or an isosceles triangle does not have two congruent sides; true.

Proportions in triangles solve for x