She makes 20 observations in all, because there are 5 groups with 4 students in each group. 5x4=20
Answer:
a = 
Step-by-step explanation:
Given
G = 4ca - 3ba ← factor out a from each term on the right side
G = a(4c - 3b) ← divide both sides by (4c - 3b)
a = 
The formula:
A = bh + L (s1 + s2 + s3)
A: area
b: base
h: height
L: length
s1: side 1 (cross-sectional area)
s2: side 2 (cross-sectional area)
s3: side 3 (cross-sectional area)
Here’s an example (see attached image)
A = (4 x 6) + (12 x [7 + 7 + 4])
A = (24) + (12 x 18)
A = 24 + 216
A = 240cm^2
I hope this helped? Comment if you need more explanation or anything!
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