We have the following information;
The world's current oil reserves is R= 1830 billion barrels and is decreasing by 20 billion barrels of oil a year.
a. We want to give an equation for the remaining barrels R in terms of time t.
The equation is ;

b. 8 years from now, the world's oil reserve would be;

c. If no other sources are discovered, the world's oil will be finished when R is zero.
Thus;
