George donated half his monthly income to charity and spent $20 from the other half on groceries. If he now has $100 left, how much was his monthly income?
Half his monthly income is $100+$20 = $
<gadget id="calculator">100+20</gadget>
<output>120</output>
120.
His monthly income therefore is 2*$120 = $
<gadget id="calculator">2*120</gadget>
<output>240</output>
240.

<result>240</result>