12.2.5 - Multiplying and Modifying Strength

Weapons may have Strength "x(X)" listed. In this case you multiply the Strength (S) characteristic of the equipped model by the value of (X) for resolving the models attacks with that weapon. Sometimes a model might receive multiple strength modifiers. Modifiers that enhance a model's Strength (S) Characteristics that are not from a weapon are applied before modifiers from weapons.

For Example: a model with Strength 4 has a piece of wargear that grants him +1 Strength, and also is under the effect of a Special rule or Power that grants him +2 strength. This same model is equipped with Strength "x2". This model has a bonus of the non weapon modifiers (+3), which is applied before a weapon modifier (x2), granting this warrior's attacks a Strength of 14 (4+3=7x2) when using this weapon.