Question

3x + 5y = 78

Answer 1

Answer:  The correct option is (B) 6.

Step-by-step explanation:  We are given to select the x co-ordinate of the point of intersection of the following lines.

$3x+5y=78~~~~~~~~~~~~~~~~~~~~~~~~~~~~(i)\\\\2x-y=0~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~(ii)$

To find the x co-ordinate of the point of intersection, we need to solve the given system of equation to find the point of intersection.

From equation (ii), we have

$2x=y\\\\\Rightarrow y=2x~~~~~~~~~~~~~~~~~~~~~~~~(iii)$

Substituting the value of y from equation (iii) in equation (i), we get

$3x+5(2x)=78\\\\\Rightarrow 3x+10x=78\\\\\Rightarrow 13x=78\\\\\Rightarrow x=\dfrac{78}{13}\\\\\Rightarrow x=6.$

Thus, the x co-ordinate of the point of intersection of the given lines is 6.

Option (B) is CORRECT.

Answer 2

Hello here is a solution :
3x + 5y = 78 .... (1)
2x - y = 0 ... (2)
from (2) : y = 2x
in (1) : 3x+5(2x) =78
            13x = 78
x= 6
 but : y =2x    y=2(6) = 12
answer : x=6