Answer:
2011
Step-by-step explanation:
Here is the formula.

A = Final Value
P = Starting Value
R = Rate
N = Time in Years
A = 8,000,000,000
P = 5,400,000,000
R = 0.0195
N = Time in Years
Solve for n.
20.35 Years from 1990; so sometime in 2011 the population would be 8 billion.
48 miles/4hrs = 12 mph
Increased Speed 12 mph + 8mph = 20 mph
Distance left 108 miles - 48 miles = 60 miles
Time left 60 miles/20 mph = 3 hours
Y = k/x
13 = k/6
k = 78
y = k/x
8 = 78/x
8x = 78
x = 78/8
x = 9.75
-10 x -5 = 50 and -10 + -5 = -15