Please show work.

Simplify. 40) 81 - 18 . 3 + 225 + (-15) 41) -43 . 10 + 2 42) 72 + 32 43) 22 + 42 - 6 44 ) ( - 6 ) 2 + ( - 2 ) 2 - 2 45) 2 - (-6) . (-3)2 46) 5 . 22 + 5 . (5 +5) - (-8) Find the value of the expression. 47) -7x - 4y - 6a for x = 3, y = 2, a =1 48) (-4x - 2y)(-3a) for x = -4, y = 1, a =-3 49) 6x + (3y)(-4a) for x = 3, y = -2, a =-3 50) (-5x + 4y)(-8a) for x = 4, y =3, a =1 51) a + (-5x - 7y)(a) for x = 1, y =2, a =2 52) 6x+ by for x=-2, y = 1, a = 0 6a + 2 53) -9x - 3y for x= -4, y = 1, a =1 a - 2