Two numbers that multiply to equal 405 but add to equal 42

X*y=405

x+y=42

y=405/x

x+405/x=42

x^2+405=42x

x^2-42x+405=0

(x-27) (x-15) = 0

x=27

x=15

27 and 15 add up to 42 and when multiplies they have a sum of 405

simply do trial and error for this type of question, try using factors of the number to find out what can be used to equal the number