Three times the larger number of two numbers is equal to four times the smaller. the sum of the numbers is 21. find the numbers

X=larger number

y=smaller number

3x = 4y

x+y=21

3x=4y

3x:3 = 4y:3

x = 4/3y

x+y=21

4/3y+y=21

1 4/3y=21

1 4/3y : 1 4/3=21 : 1 4/3

y = 9

x + y = 21

x + 9 = 21

x + 9 - 9 = 21-9

x = 12

Check

3x = 4y

3 (12) = 4 (9)

36=36