300 yuan's income was recorded as-when 240 yuan arrived in 300 yuan, it was recorded as 360 yuan.

It can be judged that when the income is negative, when it is used, it is positive (just the opposite).

Then -240/300=-0.8, that is, income 1 yuan -0.8 yuan.

Then 360/300= 1.2, which means 1 yuan1.2 yuan is used.

Then the following is very convenient ~

If 100 yuan is used, judge the plus sign first and then100 *1.32 =120 yuan.

Their benchmark is the one calculated above ~

I hope the answer can help you ~ thank you