I first calculated new E values for charges -2microC and -1microC due to the new electron on the x-axis and got: E-2= k*(2E-6)(1.6E-19)/8 and E-1=k(1.0E-6)(1.6E-19)/8. Then I calculated E values for the x-directions: Ex-2=E2*(2/sqrt8)=2.54E-16 and Ex-1=E-1*(2/sqrt8)... then I added them together...