1. Use this formula to obtain the number of integers:

(last - first) / increment + 1

(20- 2)/2 + 1 = 10 avg = (20 + 2) / 2 = 11 even integers

sum = 10* 11 = 110

same for odd

(19 - 1)/2 + 1 = 10 odd integers
(19 + 1)/2 = 10

10 *10 = 100

110 - 100 = 10


2. 1250: 4000
ratio: 6x::2x::1x

37500/1250 = 30

(6)*(5) = 30

so x is 5

since 4000 is the ratio of 1x, it is 1*5 = 5


3. 660 + 30(x) = 780 -10(x)

x = 3

so it is 1993