It is true because if a is perpendicular to b and b is perpendicular to c therefore a has to be perpendicular to c also they said that all three lines are coplanar therefore the statement must be true
I hope this helped you out :)
I'm so confused what do you need help with?
It is the first option i think
So we have the system of equations:

equation (1)

equation (2)
To use substitution, we are going to solve for one variable in one of our equations, and then we are going to replace that value in the other equation:
Solving for

in equation (2):



equation (3)
Replacing equation (3) in equation (1):






equation (4)
Replacing equation (4) in equation (3):



We can conclude that the solution of our system of equations is <span>
(7/5, 21/10)</span>