You already got the first two questions right: the group with the highest number of people unemployed / unemployment rate is the one with the highest bar in the respective histogram.
The two graph are related in this sense: take the first age group as reference. We know that 700 people from 16 to 19 are unemployed, and that those people represent 14% of the population, then we know that the 14% of the population between 16 and 19 is 700.
We can deduce that, if x is the number of people between 16 and 19, we have

So, by the relation between the two graphs, we can deduce the total population for each age group.
The differnce of 2 perfect cubes
remember
a³-b³=(a-b)(a²+ab+b²)
so
Answer:
if you solve the equation it is 8 but the equation is 5-(-3) or 5+3 because two negatives equal a plus
Five years ago:
Peter= P-5
Sam = S-5
Peter was 3 times older than Sam, which means that (P-5) = 3(S-5)
P-5 = 3S-15
So, the equation that would complete the system is C. P - 5 = 3S - 15
P-5 = 3S-15
P-3S = -15+5
P-3S = -10
So, now we use two equations: P-3S = -10 and the original one P+S=30
P-3S=-10
P+S=30 (to simplify the equation, multiply it by -1)
P-3S=-10
-P-S=-30
__________
0P-4S=-40
-4S=-40
4S=40
S=40/4
S=10
P+S=30
P+10=30
P=20
This means that Pete is 20, and Sam is 10. Hope this helps!