Explanation:
Although the scale of the graph is not given, we may assume that 1 unit refers to 1 box.
f(2) is indeed 4.
By drawing the horizontal line y = 5 onto the same graph, one can see there are 3 real solutions to f(x) = 5.
The graph is decreasing on [0, 4] as its gradient is negative throughout the interval.
g[f(1)] = g(6) = [2(6) - 7]/3 = 5/3.
No, the inverse is not a function. This was already seen by the 3 real solutions to f(x) = 5 (i.e. f^-1(5) will result in 3 output values).