This is an arithmetic sequence with a common difference of -4, meaning that each term is four less than the previous term. So the next term in that sequence (technically the term "series" should be reserve for infinite sequences) will be 67-4=63.
x+y=120_______1
x=4*y_________2
x=4y
substitute 4y for x in equation 1
`4y+y=120
5y=120
eliminate the coefficient of y
y=120/5
y=24
now,input 24 for y in equation 2
`x=4y
x=4*24
x=96
thus, the numbers are
96 and 24
