The three charges shown in the figure are located at the vertices of an isosceles triangle.?

Calculate the electric potential at the mid-point of the base if the magnitude of the
positive charge is 7.0×10−9 C and the magni-
tude of the negative charges are 5.9 × 10−9
C. The value of the Coulomb constant is
8.98756 × 109 N · m2/C2 , and the accelera-
tion of gravity is 9.8 m/s2 .
Answer in units of V

the two sides of the triangle are 5.4cm and the base is 1.4cm Please help?
due today at midnight. I don't know where to start or how to solve this problem if you could please help!..i know Q+ is 7.0 x 10-9,Q- is 5.9 X 10-9,k =8.98755 x10^9,g= 9.8m/s.

im not able to solve this equation