Which expression defines the given series for seven terms?
-3 + (-1) + 1 +
a. ∑ (5n - 2)
b. ∑ (2n - 5)
c. ∑ (5 - 2n)
d. ∑ (2 - 5n)

Solve - pv + 40 < 65 for v solve 7w - 3r = 15 for r

1) prove that 731^3−631^3 is divisible by 100 2) prove that 99^3−74^3 is divisible by 25

White shapes and black shapes are used in a game. some of the shapes are circles. while the rest are squares. the ratio of the number of white shapes to the number of black shapes is 5: 11. the ratio of the number of white cicrles to the number of white squares is 3: 7. the ratio of the number of black circles to the number of black squres is 3: 8. work out what fraction of all the shapes are circles.