Use a calculator to find the measures of b to the nearest tenth

What is the effect on the graph of the function f(x)=x when f(x) is replaced with -f(x)+4

The graph and table shows the relationship between y, the number of words jean has typed for her essay and x, the number of minutes she has been typing on the computer. according to the line of best fit, about how many words will jean have typed when she completes 60 minutes of typing? 2,500 2,750 3,000 3,250

I’m still confused on how to work the percentages