there are three sensors, A, B and C. In order for the alarm to go off, any two of the sensors have to be activated at the same time. Do a truth table for the expressions and simplify it.
First off, this post should probably be in the homework topic. Maybe the mods can move it. On to your question. This one should be pretty simple. I will not give you the answer but I will certainly lead you in the right direction. Firstly draw your matrix and consider A, B and C as binary bits. Place 1's and 0's in the matrix in a 3 bit binary counting arrangement. See if you can work it out from there.
