Physics
posted by Nina .
calculate the force between two identical charges of 1.0 x 10 exp 9 C separated by 1.0 Cm

Look up Coulomb's Law in your textbook or course notes.
F = k Q1*Q2/r^2
Depending upon which constant k you use, you may need to convert the r = 1 cm separation to 0.01 m. 
for same question above if the charge is increased by a factor of 10 what number am I increasing? and am I increasing it by adding or multiplying?

When you are talking factors. you increase by multiplying.
A factor of 10 increase in the charge increases the force by a FACTOR of 100, since the charge gets squared when the two charges are equal.