Jerry works five days a week as a waiter and earns a variable amount of tips every night. The past four nights, he earned $20, $60, $15, and $40. How much does he need to earn tonight if he wants to make an average of $50 in tips per night?
The total money Jerry needs to make for 5 days to get $50 per night is 5 nights * $50/night = $
<gadget id="calculator">5*50</gadget>
<output>250</output>
250.
His total earnings for the past four days is $20 + $60 + $15 + $40 = $
<gadget id="calculator">20+60+15+40</gadget>
<output>135</output>
135.
So, Jerry needs to earn $250 - $135 = $
<gadget id="calculator">250-135</gadget>
<output>115</output>
115 in tips tonight.

<result>115</result>