[求助]模考做到的一道题，看不懂哪

妙妙cathy

Before being simplified, the instructions for computing income tax in Country R were to add 2% of one's annual income to the average of 100 units of country R's currency and 1% of one's annual income. Which of the following represents the simplified formula for computing the income tax, in country R's currency, for a person in that country whose annual income is I? 

答案是50+I/40   

尤其是划线部分什么意思哪？？

isaxi

add 2% of one's annual income to 2%I
the average of 100 units of country R's currency and 1% of one's annual income
(100+1%I)/2
2I/100 + 50 + 1/200I = 50 + I/40

tydlyx

题目是说把2% of one's annual income，也就是2%I，加到100 units of country R's currency 和1% of one's annual income的平均数上，也就是（100+1%I）/2，所以整个式子就是（100+1%I）/2+2%I，化简就是答案了~~