Meta Developer interview questions

I faced three 1 on 1 interview rounds, each with one coding question. Round 1: Given an undirected graph and a node, modify the graph into a directed graph such that, any path leads to one particular node. Round 2: Given a matrix of size mXn, and a list of cells, find the number of paths from the top left cell to the bottom right cell. Round 3: Solve a linear equation in one variable, where the possible operands are +,- and * along with brackets. For eg. (2x + 5 - (3x-2)=x + 5) The interviewers themselves were very helpful, prodding me towards the right answer, and it was a good experience overall