This is an algebra solved problem, lets write an equation which describes the info presented in the problem statement, so the total earnings is $77 and those consisted of one item of $29 and the rest (77 - 29) consisted of x number of $16 items, that is:
16x + 29 = 77
So we have to isolate the x from the equation to solve it:
16x = 77 - 29 = 48
x = 48/16
x = 3
therefore, there were sold 3 paintings of $16
