Question

x+y=7 and 10y+x+3=(10x+y) find the value of y and x

Answer 1

9y -9x +3 =0
x+ y = 7

9y + 9 x = 63

-18x =-66
x= 11/3

y= 7-11/3=10/3

Answer 2

$x + y = 7 - - - - (1) \\ 10y + x + 3 = (10x + y) \\ 3 = 10x + y - 10y - x \\ 9x - 9y = 3 - - - - (2) \\ from \: 1st \\ x + y = 7 \\ x = 7 - y \\ put \: the \: value \: of \: x \: in \: eq \: (2) \\ 9x - 9y = 3 \\ 9(7 - y) - 9y = 3 \\ 63 - 9y - 9y = 3 \\ 63 - 18y = 3 \\ 63 - 3 = 18y \\ 18y = 60 \\ y = \frac{60}{18} \\ y = 3.33$
$now \\ put \: the \: value \: of y in \: eq(1) \\ x + y = 7 \\ x + 3.33 = 7 \\ x = 7 - 3.33 \\ x = 3.67$

$x = 3.67 \: and \: y = 3.33$