Alright, lets get started.
Maria hiked the 5 mile Mountain Trail a number of times and she hiked the 10 mile canal trail several times.
x times she hiked 5 mile mountain.
So, number of mils she hiked for 5 miles will be = 5 x
Similarly,
y times she hiked 10 mile canal,
So, number of miles she hiked for canal = 10 y
So, total number of miles she hiked = 
But as per question given, she had a total of 90 miles
It means

Dividing this equation with 5

So, the equation is
: Answer
Hope it will help :)