For the first problem, the triangle is equilateral. This means that all three sides will have the same length. So you need to find a value for x that makes all three of those statements equivalent. I believe you could find it using a system of equations... but it’s been a while so don’t quote me on that.
For the second, ce and de are equal. Set them equal to each other and solve for x. Then plug that x value back into the side lengths.