Step-by-step explanation:
Sn=n/2(2a+(n-1)d)
910=n/2{2a+(n-1)d}
1820=n{2a+(n-1)d}
1820=20{2a+(20-1)d}
1820=20{2a+19d}
91=2a+19d
An=a+(n-1)d
95=a+(20-1)d
95=a+19d
91=2a+19d
---------------
4=-a
a=-4
91=2a+19d
91=2(-4)+19d
91=-8+19d
91+8=19d
99=19d
d=99/19
A=-4
186cm
You add all the sides up, so 42+42+51+51 which equals 186cm
24v9w9 + 28v5w7y8
Also sub to Stariceie E
The answer is A. I plugged it into a TI-83 calculator. If you need to know how I did that I will be happy to help
