Answer:
D
Explanation:
Why A is wrong:
If a friend has $30 in his checking account and he made a purchase of $28, the equation would be:
30-28 = $2, which does not equal zero.
Why B is wrong:
The temperature was zero and went down to negative ten. It went up to 10, not zero. So this is also wrong.
Why C is wrong:
A friend borrowed $20 dollars and promised to return double the amount, $40. The equation for this is:
20 - 40 = -20, which also does not equal zero
Why D is correct:
Income is how much you earn
Expenses is how much you pay.
If both of them are equal, then your income is zero, which is the correct answer.
Hope this helps :)
-jp524