An equilateral triangle has sides of 0.16 m. Charges of -8.8, +8.0, and +1.7 µC are located at the corners of the triangle. Find the magnitude of the net electrostatic force exerted on the 1.7-µC charge.
Definitely the wrong forum.
But, all you need is Coulomb's law.
$\displaystyle F = \frac{1}{4\pi\epsilon_0}\left( \frac{q_1q_2}{r_2^2} + \frac{q_1q_3}{r_3^2} \right)$
Since its an equilateral triangle, r is the same for each:
$\displaystyle F = \frac{q_1}{4\pi\epsilon_0 \cdot r^2}\left( q_2 + q_3\right)$
You can do the plug and chug.