Please help me in solving this attached problem.Explain how you solved........thank you

@ sunkari 
the question posted by you can be solved by the use of the besic formula 
E= kq/ rsquare . 
you can find out the electric field intensity , 
as here the charges are of same sign and diffrent magnitude , then just apply that formula for finding E1 nd E2 and then take the average , u can calculate the lectric field intensity in the midway . 
and remember – if the chrges are of same magnitude and of same sign , then the electric field intensity is 0 in the centre . 

HOPE U CAN SOLVE IT NOW 
IF NOT THEN LET ME KNOW 
ALL THE BEST ..