Answer:
-4a + 7a = + 3a
But you don't actually need a pkus sign 3a is fine too. You are basically sum - 4 and 7. Let me know if you still confused.
There is a 1/3 chance. Add up the shaded parts for a total of 120 degrees. 120/360 is 1/3
Zero property because you are using zeros to multiply
Original price is $150 so you times 150 by 0.40
150 x 0.40 = 60
So you take the $150 and you subtract $60 from $150
150 - 60 = 90
So the answer is $90