The ratio of Gracie's rate of typing is 240 for every 6 min, but what about per minute? You can divide 240 by 6 and get 40. It'll be easier that way.
sLet's use for example n = 9 we want to know how many words Gracie can type in nine minutes. Using the key 40 per minute we can use an expression n x 40 = w
I got this by taking the 3 test scores that were provided and adding them then subtracting that by 360 (90x4 - which would give you a 90 in the end) so I had 360 - 262 which equaled 98 and that would be the score needed to have a 90 in the end.