Answer:
= 1
Step-by-step explanation:
The n th term of an arithmetic progression is
= a + (n - 1)d
where a is the first term and d the common difference
use the 9 th term and 7 th term to find a and d
= a + 8d =
→ (1)
= a + 6d =
→ (2)
Subtract (2) from (1) term by term
2d =
⇒ d = 
Substitute this value into (2) and solve for a
a +
= 
a =
-
= 
Hence
=
+
= 1
Answer:103°
Step-by-step explanation:
because do the math
let the exterior angle be x
x=60°+80°(being one exterior angle is equal to two interior angle)
x°=140°
Answer:
The cost of the old ball was $100.
Step-by-step explanation:
The cost of the new ball = $300
The new ball has three times the price of his old ball.
So, let the price of the old ball be = x
As per situation, we get the equation:

Dividing both sides by 3:

=> x = 100
Hence, the cost of the old ball was $100.
((5x2)+5.5+(6x3)+6.5+(7x5)+(7.5x4)+(8x4))/20
137/20
= 6.85