Need an answer quick (giving brainliest)

Which shows the correct solution of the equation 1/2a+2/3b=50, when b=30?

The length of the line segment joining the midpoints of sides ab and bc of the parallelogram abcd is 10. find the length of diagnol ac

If set d is not the empty set but is a subset of set e, then which of the following is true? d ∩ e = d d ∩ e = e d ∩ e = ∅