Miles had three sets of building blocks.His first sett had 491 pieces.His second sett had 624 pieces.Miles combined his three sets for a total 1374 pieces. How many pieces had been in his third?

259

Step-by-step explanation:

491+624=1115. 1374-1115=259

B(-1,-3)

Step-by-step explanation:

let the coordinates of B be (x,y)

Mid point of AB = (x₁+ x₂/2,  y₁+y₂ /2)

                           = (-3 +x/2 , -5+y/2)

Mid point of AB is  M(-2,-4)

(-3 +x/2 , -5+y/2) = (-2, -4)

-3 + x /2 = -2       ; -5+y/2 = -4

    -3 + x = -2 * 2 ;    -5 + y = -4 * 2

       -3 + x = -4    ;     -5 + y = -8

            x = -4 +3 ;    y     = -8 +5

            x = -1       ; y = -3

B(-1,-3)