A–4.0-µc charge is located 0.45 m to the left of a +6.0-µc charge. what is the magnitude and direction (to the right or to the left) of the electrostatic force on the positive charge?

Attraction (right?), so the + charge will try to go to the - charge. Force on  + charge will be directed towards left. The magintude is Coulomb's law:

F = k * Q1*Q2/d^2, K = 9*10^9, Q1 = -4*10^(-6), Q2 = 6*10^(-6), and d = 0.45

-9*4*6*10^(-3)/0.45^2 = -1.0633 N, but check it (sign means attractive).

Some teachers prefer to say that magnitude is always positive, like in math, so 1.0633 N but then say attractive and directed to the left of the + charge, to make sure no one can complain you miss anything! Ask your teacher

The answer would be a