Mr. edward's buys 2 new knobs for each of his kitchen cabinets. the kitchen has 9 cabinets. how many knobs does he buy?

Liz had 140 pens and inna had 100 pens. after inna gave liz some pens, liz had 3 times as many pens as inna. how many pens did inna give liz?

If the altitude is drawn to the hypotenuse of a right triangle, then the two triangles formed are similar to the original triangle and to each other. which set of triangles shows the similar triangles created by the altitude in the diagram?

The function f(x)= -(x+5)(x+1) is down. what is the range of the function?