very good idea to draw a picture as steamking said.
Another approach is to express the direction of the vectors with ##\hat{i}## and ##\hat{j}## components, where ##\hat{i}## represents the x-direction of the vector and ##\hat{j}## represents the y-direction of the vector.
Here is the concrete demonstration of the vectors: If a vector points to the right, then we obtain the positive ##\hat{i}## component. If a vector points up, then we obtain the positive ##\hat{j}## component. From here, we see that if a vector points up and right, then we obtain both positive ##\hat{i}## and ##\hat{j}## components.
Remember, when combining vectors, you have to add their magnitudes component-wise as you do with variables in pre-calculus class.
Note: The combination of those two vectors don't give you the answer you want since it points up-right. You need to figure out the vector ##\vec{c}## in which ##\vec{a} + \vec{b} + \vec{c} = 0##
