Matt walker is paid weekly and earns 3.5% straight commission on sales of $6,500 or less and 5% on sales in excess of $6500.last week, matt total graduated commission was $415. what were his total sales for the week?

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"