Ineed with this math problem. i am confused on how to do it. if you could me it would be great. there are 2 parts to this problem. i need with both problems. 

She took a total of 60 minutes
she answered both mulitiple choice and extended response in the total time which is 60 minutes
she took 2 minutes on rach multiple choice question and 6 minutes for the extended response
let x=number of multiple choice questions
let y=number of extended response questions
we can deduce that
total time =x*2+y*6
60=2x+6y
also we can deduce
20=x+y
since 20 ia the sum of multiple choice and extended response
for part 2 we just solve the system of equations
60=2x+6y
20=x +y
lets multiply the second equation by 2 so we can get rid of x
60=2x+6y
40=2x+2y
subtracting the two equations from each other to yields
20=0 +4y
y=5
to get x we substitute in one of the equations we derived from question 1
x+y=20
substituting y for its value we get
x+5=20
x=15