the given expressions are,
x + 7y = 23 ....... (1)
3x + 14y = 48 .......(2)
multiply the equation 1 by 3
3x + 21y = 69
3x + 14y = 48
subtract the equation
3x+ 21y - (3x + 14y ) = 69 - 48
3x + 21y - 3x - 14y = 21
7y = 21
y = 21/7
y = 3
put y = 3 in equation 1
x + 7 (3) = 23
x + 21 = 23
x = 23 - 21
x = 2
thus the asnwer is x =2 & y = 3