Because like terms you add or subtract together to make it easier to do the problem. just like you do with whole numbers. you add an subtract to make the answer simpler.
The hardest part is finding the length of the curve at the top. To find arc length, multiply the circumference by the arc angle divided by full angle (360°) in a circle. Or:

x, the arc angle in a semicircle, is 180°.
r, the radius is 7/2 = 3.5.
Now just plug the numbers in and solve for arc length, s.
s = 2π(3.5)(1/2) ≈ 11.00
Now just add up all the sides. 11cm + 10cm + 10cm + 7cm = 38 cm.
Answer:
Friend 1: $11.53 Frind 2: $5.21 Friend 3: $5.21
Step-by-step explanation:
15.63/3=5.21
One friend pays for the rest.
1.29*3=$3.87=drinks
salad=$2.45
5.21+3.87+2.45=11.53
From x equals five to nine, the y value changes as follows
+10,+2,+1,+3
Assuming that "average" implies the mean, the sum of all four values is 15. Then divide 15 by the four values added = 15/4 = 3 3/4 or 3.75