The problem
Click to see the original problem
Please explain the third to last step and how worked denominator in last step. Thanks
Answer provided by our tutors
In the third step, the numerator comes from:
while the denominator comes from:
To get to the fourth step we cross-multiply from the third step:
and get (pay attention that 10 is written as 2*5, and 4 is written as 2*2):
Next, we divide the numerator and denominator by 
and get:
and finally, after doing the calculations, we arrive to the solution:
