Please please please help algebra 2

X+ y = 5 ; x - y =3 solve using linear combination

Someone answer asap for ! the following statements are true about the coins calvin and sasha have collected. * calvin and sasha has the same amount of money. * calvin has only quarters. * sasha has dimes, nickels, and pennies * calvin has the same number of quarters as sasha has dimes. * sasha has $1.95 in coins that are not dimes. exactly how many quarters does calvin have?

An airplane travels at an unknown elevation before it descends 3 miles to an elevation of 15 miles. find the elevation of the plane before its descen.