Which ordered pair is the solution to the system of equations?
a. (1, 7)
b. (4, 9)
c. (7, 19)
d. (8, 21)

I could just give you the answer but you should know how so you don't need my help :)

Solve by substitution.

Step 1: Set the first equation to y by isolating the y term.

2x-y=-5
2x+5=y (see how that worked? I flipped the signs of the numbers and moved them)

Step 2: Substitute the new equation for y in the second equation.

x+3y=22 -> x+3(2x+5)=22 (now lets simplify)
7x+15=22 (I distributed and added like terms) (now we can isolate that pesky x term)
7x=7 (now its trickier than just flipping the sign, now i have to divide x by 7 since it is multiplied by 7)
x=1

Step 3; Substitute the new x answer into the original first equation

2x-y=-5 -> 2(1)-y=-5 (Lets isolate now since we already know that 2x1 is 2.)
-y=-7 (lets cancel out those signs to finish the isolation)
y=7

So your answer is 1,7

3were boys and 5 were girls