Answer:
(d) 5i -j
Explanation:
You want the value of the expression 2u -v where u=3i and v=i+j.
Substitution
Use the given definitions of u and v, and simplify in the usual way.
2u -v = 2(3i) -(i+j)
= 6i -i -j . . . . . . . . . eliminate parentheses
= 5i -j
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Additional comment
The unit vectors i and j can be treated as though they were variables. The usual properties of equality and (scalar) arithmetic apply.