Answer:
The length side of the triangle is 
Step-by-step explanation:
we know that
The equilateral triangle has three equal sides and three equal internal angles of measure of 60 degrees each.
Let
b------> the length side of the equilateral triangle
Applying Pythagoras theorem
-10, -10-2·1= -12, -10-2·2=-14, -10-2·3=-16, -10-2·4= -18, -10-2·5= -20,
-10-2·6= -22, -10-2·7 =-24, -10-2·8=-26, -10-2·9=-28
a=-10
d=-2
xn=a+d(n-1)
the first ten terms are
-10, -12, -14, -16, -18, -20, -22, -24, -26, -28
Actually the answers A since t is for text messages and it costs .15 and m is minutes and costs .07 so we add those two together to he .15t+ .07m then there's a discount of 2.50 so we subtract. So our final equation is .15t + .07m - 2.50 = C
