That "1" in front of the parentheses is unnecessary and looks strange. Are you sure it isn't v= 1/(3t+ 2)?
In any case, you are told exactly what to do in the problem:
Approximate the displacement of the object on the interval by subdiving the interval into the indicated number of subintervals. Use the left endpoint of each subinterval to compute the height of the rectangles
v=1(3t+2) (m/s) for 0 ≤t ≤8, n=4
Dividing 0 to 8 into 4 subintervals means [0, 2], [2, 4], [4, 6], and [6, 8]. Although the height of the function varies continuously, you are told to "use the left endpoint of each subinterval to compte the height". So you are approximating the area under the curve by 4 rectangles, each with length 2 and heights calculated at t= 0, 2, 4, and 6.
If v really is 1(3t+ 2) then those heights are 1(3(0)+ 2)= 2, 1(3(2)+ 2)= 8, 1(3(4)+ 2)= 14, and 1(3(6)+ 2)= 20. What are the areas of those four rectangles? What is the total area. But if v= 1/(t+ 2), the heights are 1/(0+ 2), 1/(2+ 2), 1/(4+ 2), and 1/(6+ 2). What are the areas of those rectangles? What is the total area?