To find the electric potential at the origin you would need to add up the electric potentials of the two point charges affecting it, namely q1 and q2.

The formula for electric potential of point charge is

V = (ke*q)/r

Now you must apply this equation to q1 and q2:

V1 = (ke*q1)/r1 and V2 = (ke*q2)/r2

plug in the values which are:

where ke = 8.988*10^9 N*m^2/C^2

q1 = 3.3*10^-6 C

q2 = -2.14*10^-6 C

r1 = 1.25*10^-2 m

r2 = -1.8*10^-2 m

plug these values into the formula above, and add V1 and V2 to find the total electric potential

For more help check out these questions:

http://answermenu.com/?qa=223/point-charge-origin-and-point-charge-located-along-the-axis

http://answermenu.com/?qa=244/find-the-electric-potential-at-point-a