Let the missing number be x,
For the first question, the equation is as follows,
x - 13 = 29
Solve for x,
x - 13 + 13 = 29 + 13
x = 42
The equation would then be 42 - 13 = 29
For the second question, the equation is as follows,
x - 12 = 203
Solve for x,
x - 12 + 12 = 203 + 12
x = 215
The equation would then be 215 - 12 = 203