Angle JMS is 180-59=121 degrees, not 73. Angle J is 180-90 (angle E) which is 90. Now subtract 48 from 90 (because of Angle A) and you get 42, so angle J is 42. 180-121-42=17, so angle JSM is 17 degrees. Basically you have to remember that 180 is the total sum of a triangle's angle degrees. I hope this helps