Answer:
Suppose that we have a given point (x, y)
If we translate this point N units to the right, then the new coordinates of the point are:
(x + N, y)
Ok, now if we know that the vertices of the trapezoid are:
(1, 2), (3, 1), (3, 5), (1, 4)
And we move the whole figure 4 units to the right, then all the vertices are moved 4 units to the right.
Then the new vertices of the figure will be:
(1 + 4, 2) = (5, 2)
(3 + 4, 1) = (7, 1)
(3 + 4, 5) = (7, 5)
(1 + 4, 4) = (5, 4)
Then the coordinates of the image of the trapezoid (of the new vertices) are:
(5, 2), (7, 1), (7, 5), (5, 4)
, 
and the solutions are decreasing functions.