Determine Whether an Ordered Pair is a Solution of a System of Equations. In the following exercises, determine if the following points are solutions to the given system of equations.
$$
\left\{\begin{array}{l}
x+y=2 \\
y=\frac{3}{4} x
\end{array}\right.
$$
(a) $\left(\frac{8}{7}, \frac{6}{7}\right)$ (b) $\left(1, \frac{3}{4}\right)$