To be clear I understand:
Dorothy types 120 words per minute.
let's say that her rate per minute = x
x*1 =120//divide by 1:
x=120
for 1.75 we have the following equation:
x*1.75=y
where we have to find y.
we know that x=120
so we have:
120*1.75=y
120*(1+0.75)=y// (0.75 of 120 is 90. We can find it by diving 120 by 4 (30) and multiplying by 3 (3*30=90)).
120+90=y
210=y
so she can type 210 words per 1.75 minutes.
Let me know if youy have further questions!