Given that measure of angle a=(5y+11), measure of angle d = (12y-10), measure of angle e=51, and measure of angle f= (30y+13), find measure of angle a

If there are 4 angles here, then I'm assuming this is a single 4-sided figure, which is a quadrilateral.  All the angles of a quadrilateral add up to equal 360.  Therefore, 5y+11+12y-10+51+30y+13=360.  Combining like terms we get 47y+65=360.  And 47y = 295  y = 6.276595.  That's odd, but we will continue on...angle A then is 5(6.276595)+11 which is 42.38297 if what you typed was actually correct.