Well, 6/8 can be simplified: divide the numerator and denominator by 2, then your simplified fraction is 3/4. Now, multiply straight across: 4 times what=12? 3 does. So, you do the same thing to the numerator, because whatever you do to the denominator must be done to the numerator, and same reversed. 3*3=9, so the answer to this is 9/12!!
If you're looking for the solution to the system of equations, here's how we solve using substitution
We know that y = x - 1, so we can plug that into the first equation giving
2x - 3(x-1) = -1
Now distribute the 3 giving 2x - 3x + 3 = -1. After combining like terms we get -x + 3 = -1. Now subtract 3 from both sides, -x = -4, and multiply both sides by -1 to make x positive. x = 4
Now we can plug that into the second equation to get y
y = x - 1, and we know that x = 4, so y = 4 - 1, y = 3. The solution is (4, 3)
Answer: Choice A) Triangle ABC is similar to triangle ACD by AA
AA stands for Angle Angle. Specifically it means we need 2 pairs of congruent angles between the two triangles in order to prove the triangles similar. Your book might write "AA similarity" instead of simply "AA".
For triangles ABC and ACD, we have the first pair of angles being A = A (angle A shows up twice each in the first slot). The second pair of congruent angles would be the right angles for triangle ABC and ACD, which are angles C and D respectively.
We can't use AAS because we don't know any information about the sides of the triangle.

The rational values are :
and
The Irrational values are :
and