Answer:
b=8
Step-by-step explanation:
b²+15²=17²
b²+225=289
b²=289-225
b²=64
b= 8
I hope I helped you^_^
The general formula for the lateral surface area of a regular pyramid is:

Where:
p=perimeter of a base
l=slant height
a.
a=3ft
l=4ft
p=5*a=5*3=15ft

b.
a=2.5ft
l=4ft
p=6*a=6*2.5=15ft

c.
a=1.9ft
l=4ft
p=8*a=8*1.9=15.2ft

d.
Based on a lateral surface area the blue umbrella is best choice. But, the best umbrella overall is the one with the greatest base area. General formula for regular polygon is:

For pentagon:
A=15.48ft^2
For hexagon:
A=16.24ft^2
For octagon:
A=17.43ft^2
Blue umbrella is still best choice.
Step-by-step explanation:
169 - 9 = 160
.............
Its 9.5 Also i like Trains 190 ÷ 21 = 9.5
Mean=average=sum of terms/number of terms...
(25+17+38+11+24)/5
115/5
23