So basically all you do it answer a question
Let the two numbers be x and y, then
x - y = 48 . . . (1)
x + y = 60 . . . (2)
(1) - (2) => -2y = -12 => y = -12/-2 = 6
From (1), x - 6 = 48 => x = 48 + 6 = 54
Therefore, the two numbers are 54 and 6.
The two angles form a straight line and need to equal 180 degrees
180 - 61 = 119
The missing angle is 119 degrees
Basically you know that the 2 wholes from both sides cancel out.
Set up the equation, 5/8 = 3/12 + 3/x
3/x = 5/8 - 3/12
Set them to have a common denominator, 3/x = 15/24 - 6/24
3/x = 9/24
Simplify 9/24 and you will get 3/8
3/x = 3/8
Obviously this means x = 8