Three collinear charges +7.0 x10^-5 C , +4.8 x10*-5 C, and -8.0 x 10^-5 C exert forces on each other. The first and second charges are 35.0 cm apart. The second and third charges are 35.0 cm apart. What is the magnitude and charge of the total force on the third charge?
I know the answer is F=-380 N , but I'm confused on how to get the answer.