Question

It 4x + 7y = 9 and 7x + 4y=2 then what is the
value of x + y?​

Answer 1

Answer:

x + y = 1

Step-by-step explanation:

1) Simplifying the value of first equation to get value as x

4x + 7y = 9

4x = 9 - 7y

x = (9 - 7y) / 4

2) Substituting the value of x in the second equation to get value of y

7 * (9-7y / 4) + 4y = 2

(63 - 49y) / 4 + 4y = 2

(63 - 49y) / 4 = 2 - 4y

63 - 49y = 4 * (2 - 4y)

63 - 49y = 8 - 16y

49y - 16y = 63 - 8

33y = 55

y = 55 / 33

y = 5 / 3

3) Finding the real value of x now that we have the whole value of y by substituting

4x + 7 * (5 / 3) = 9

4x + 35 / 3 = 9

4x = 9 - 35 / 3 (35 / 3 is a term not to be mixed with 9 - 35 / 3 as a whole term)

4x = (27 - 35) / 3

4x = -8 / 3

x = -8 / 3 * 4

x = -8 / 12

x = -2 / 3

4)  Finding the value of x + y since we have values of x and y

x + y = -2 / 3 + 5 / 3

x + y = (-2 + 5) / 3

x + y = 3 / 3

x + y = 1

Hope it helped :D