find the value of x and y first and use this later to get the result of given expression.

Correct Option: D

we have, x + y - 7 = 0
⇒ x + y = 7 ...(i)
and 3x + y - 13 = 0
⇒ 3x + y = 13 ..(ii)
By subtracting Eq. (i) from Eq. (ii), we get
3x + y = 13
x + y = 7
----------------------
2x = 6 ...(ii)
∴ x = 3

On putting the value of x in Eq. (i), we get
3 + y = 7
∴ y = 4

Now, 4x² + y² + 4xy
= 4 x (3)² + (4)² + 4 x 3 x 4
= 4 x 9 + 16 + 48
= 36 + 16 + 48 = 100

3x + 7y = 75 ..(i)
5x - 5y = 25
∴ x - y = 5 ...(ii)
On multiplying Eq. (ii) by 7 and adding to Eq. (i), we get
3x + 7y = 75
7x - 7y = 35
------------------
10x = 110
x = 11

Correct Option: D

3x + 7y = 75 ..(i)
5x - 5y = 25
∴ x - y = 5 ...(ii)
On multiplying Eq. (ii) by 7 and adding to Eq. (i), we get
3x + 7y = 75
7x - 7y = 35
------------------
10x = 110
x = 11
∴ Putting the value of x in Eq. (ii), we get
11 - y = 5
∴ y = 6
∴ x + y = 6 + 11 = 17