30+70÷8÷5-1=
=30.75
hope this helps
Answer:

Step-by-step explanation:
(This exercise is presented in Spanish and for that reason explanation will be held in such language)
El lado restante se determina por la Ley del Coseno:



Finalmente, el angulo C se halla por medio de la misma ley:




The set is not closed
Example:
-4 * -3 = 12 this is not a negative integer
under a rotation about the origin of 180°
a point (x, y ) → (- x, - y )
hence D is correct, both the x and y coordinates of the points on ΔA'B'C' have opposite signs from the corresponding points on ΔABC