The equation would be E =20H. E means her total earnings. 20 is how much money she earns per hour. H is how many hours she tutors. If you put it all together, you get E = 20H.
To solve how much she would get for 15 hours, plug in 15 for H so E=20(15). 20 x 15 = 300. Therefore, she will get $300 after teaching for 15 hours.
A fraction. I.E. : 6 has 36 parts (6 parts per one) If you took 2 out of the six parts away you would get 32/6 or 5 2/6 (2/6 could be simplified to 1/3)