Answer:
a. 16
b. 26
c. (11,13) and (17,19)
d. 3,8,12
Step-by-step explanation:
1. 2x8 = 16, sum of 1 +6 ( 2 digits)= 7
2. 2+3+5+7+11= 28
3. 10 to 20 ( 11,13,17,19) so we can make a pair that has difference of 2 like (11,13)
4. I will attach
2x+4x=6x
6x+3=15
6 multiplied by 2 = 12
12 +3=15
so x =2