I believe that the answer is B.
His total sales were "x"
now, we know that 3.5% of "x" plus 5% of "x", will add up to his total commission, including sales of 6500 or less or more
so the commission for 6500 or less, is 3.5% of "x" or (3.5/100)*x -> 0.035x
the commission for above 6500 is 5% or (5/100) * x --> 0.05x
we know, that both commissions added together, are $415
thus
0.035x + 0.05x = 415 <----- solve for "x"
Answer:
If Anne’s age is represented by the variable a then express Jenny’s age in terms of a if Jenny is three years less than half of Anne’s age