I got this question if you simplify 5(2x-7y)-4(y-3x) the answer is -22x-31y but when I work it out I got -2x-31y the mistake is that after I used the distribution law I got 10x-35y-4y-12x
but the calculator said that it is 10x-35y-4y+12x why was the minus changed into a plus