A1: first when solving an equation like such you have to put it in order so (^)means square or what ever power
6x^2-x^2-5x+3x then you combine terms,6-1=5--> 5x^2, -5+3=-2--> -2x, thus making the equation 5x^2-2x so the answer is c
a2: out of the choices we can see that they all have x variables but 3xy is different from the other terms because they do not carry a y variable making 3xy the term that cannot be combined with the others