Hey there!
To make this easier, we need to transform the numbers in decimal
3/4 = 0.75
1/5 = 0.2
So Martina walks 0.75 miles in 0.2 hour. They want us to find how far will she wake in 1 hour.
So we say:
0.75......>0.2 hr
x...........1 hr
Cross multiply
0.2 * x = 1 * 0.75
0.2x = 0.75
x = 0.75/0.2
x = 3.75
Martina will work 3.75 miles in one hour.
I hope this helps!