Data Sufficiency

Dave and Matt were among those people who sold tickets for Magna's concert. If they sold a total of 90 of the tickets, how many of the tickets dis Matt sell?

(1) Dave sold 30 tickets more than Matt.
(2) Matt sold 50 percent of the tickets that Dave sold.

The OA is D.

Please, can any expert assist me with this DS question? I don't have it clear and I appreciate if any explain it for me. Thanks.

AAPL wrote:Dave and Matt were among those people who sold tickets for Magna's concert. If they sold a total of 90 of the tickets, how many of the tickets dis Matt sell?

(1) Dave sold 30 tickets more than Matt.
(2) Matt sold 50 percent of the tickets that Dave sold.

The OA is D.

Please, can any expert assist me with this DS question? I don't have it clear and I appreciate if any explain it for me. Thanks.

If 'D' is the number of tickets Dave sells and 'M' is the number of tickets Matt sells, then we know that D + M = 90. We want M.

1) This tell us D = M + 30. Along with D + M = 90, we have 2 linear equations and 2 variables, so we know we can solve for both variables. No need to actually do it.We can find M. Sufficient.
(But if you were dying to do a little algebra, we can substitute M + 30 in place of D in the original equation to get M + 30 + M = 90, 2M = 60, or M =. 30)

2) This tell us that M = .5D. Again, alone with D + M = 90, we have 2 linear equations and 2 variables, so we can solve for both variables. Sufficient.
(.5D) + D = 90 ---> 1.5D = 90 ---> D = 60, so M = 30.)

The answer is D