Q1. Let $W1=\bigl\{\begin{bmatrix} a & a\\ b & a\end{bmatrix}\mid a,b\in\mathbb{R}\bigr\}$ and $W2=\bigl\{\begin{bmatrix} c&d\\ e& 0\end{bmatrix}\mid c,d,e\in\mathbb{R}\bigr\}$.
Q2. Let $W1=\bigl\{\begin{bmatrix} a & a\\ b & b\end{bmatrix}\mid a,b\in\mathbb{R}\bigr\}$ and $W2=\bigl\{\begin{bmatrix} c&c\\ c& d\end{bmatrix}\mid c,d\in\mathbb{R}\bigr\}$.
Q3. Let $W1=\bigl\{\begin{bmatrix} a & 0\\ a & c\end{bmatrix}\mid a,c\in\mathbb{R}\bigr\}$ and $W2=\bigl\{\begin{bmatrix} 0&b\\ 0& 0\end{bmatrix}\mid b\in\mathbb{R}\bigr\}$.
Q4. Let $W1=\bigl\{\begin{bmatrix} a & b\\ a & b\end{bmatrix}\mid a,b\in\mathbb{R}\bigr\}$ and $W2=\bigl\{\begin{bmatrix} c&c\\ d& d\end{bmatrix}\mid c,d\in\mathbb{R}\bigr\}$.
QUESTION: Find a basis for $W1 \cap W2$ for each of the four questions.
Attempt:
For each, I equated them to each other but dont know what to do after this. Do I set up a matrix and solve?
A1. $W1\cap W2 = \bigl\{\begin{bmatrix} 0 & 0\\ b & 0\end{bmatrix}\mid b\in\mathbb{R}\bigr\}$ so its basis is $\bigl\{ \begin{bmatrix} 0 & 0\\ 1 & 0\end{bmatrix} \bigr\}$.
A2. $W1\cap W2 = \bigl\{\begin{bmatrix} a & a\\ a & a\end{bmatrix}\mid a\in\mathbb{R}\bigr\}$ so its basis is $\bigl\{ \begin{bmatrix} 1 & 1\\ 1 & 1\end{bmatrix} \bigr\}$.
A3. $W1\cap W2 = \bigl\{\begin{bmatrix} 0 & 0\\ 0 & 0\end{bmatrix} \bigr\}$ so its basis is $\varnothing$.
A4. $W1\cap W2 = \bigl\{\begin{bmatrix} a & a\\ a & a\end{bmatrix}\mid a\in\mathbb{R}\bigr\}$ so its basis is $\bigl\{ \begin{bmatrix} 1 & 1\\ 1 & 1\end{bmatrix} \bigr\}$.