7x-7-2x-2+3x-12=8x-21
I think
If Hannah gives her younger sister 3 shirts, it does not matter what order she hands them to her. No matter the order, it will still be the same group of 3 shirt. Since order is not important this problem can be solved using a combination.
Specifically we are asked to find 8C3 (sometimes called "8 choose 3"). This is a fraction. In the numerator we start with 8 and count down 3 numbers. In the denominator we start with 3 and count all the way down to 1. Thus we obtain,
4 + 3 * (7 - 2)
4 + 3 * 5
4 + 15
19 <==
Answer:
16 cities
Step-by-step explanation:
if 5days = 10 cities
8days=?
applying cross multiplication :
(8days × ten cities )÷5 day
= 16 cities