please show work. trying to learn. Thank you.

1.The probability distribution for the random variable x is displayed in the following table:

xi 13 8 - 5 9 10

pi 0.20 0.25 0.30 0.10 0.15

Find the expected value E(X) .

2. Solve the system of equations using substitution, elimination by addition, or augmented matrix methods (your choice).

2???? + 5???? = 3

3???? + 7???? = 5

3. For the linear equation 6x-7y=84:

a. Determine the slope: _______________________

b. Determine y - intercept if it exists: _______________________

c. Express equation in slope-intercept form:

4. Let n(A)=70, n(B)=90, n(A U B)=120, and n(U)=200.

a. Determine n(B') : ___________________________________

b. Determine n(A n B) : ___________________________________

c. Determine n(A' n B'): ___________________________________