Acertain number is subtracted from 20. the result multiplied by 3 is equal to 45. what is the number?

Mrs. morton has a special reward system for her class. when all her students behave well, she rewards them by putting 3 marbles into a marble jar. when the jar has 100 or more marbles, the students have a party. right now, the the jar has 24 marbles. how could mrs. morton reward the class in order for the students to have a party?

Me asap! what is the slope of this line? enter your answer in the box.

The measurement of one angle of a right triangle is 42° what is the measurement of the third angle? (there is no picture)