Answer:
i think 4 is b
Step-by-step explanation:

The given pair of angles are vertical opposite angle pair so, they are equal. i.e
(a,7) lies on the equation of 5x-y=8, that means we solve for x when y=7.
5x-(7)=8
5x=8+7=15
x=3
=>
a=3
Answer:
Infinitely many solutions.
Explanation:
In this case we gonna use ELIMINATION BY ADDITION method.For that first we are gonna eliminate the terms containing ( X ).
Equation no 1:
3x + 3y = 10
Equation no 2:
-9x - 9y = -30
Now multiply equation no 1 with (3 )
3(3x + 3y) = 3(10)
9x + 9y = 30 ( equation no 1 )
Now ADD both the equations
9x + 9y = 30
<u> -9x - 9y =-30</u>
0 = 0