SOLUTION
Given the question, the following are the solution steps to answer the question.
STEP 1: Represent the given statements.
Let x represent Tanya
Let y represent Sanjay
STEP 2: interpret the statement
From first statement,

From second statement,

STEP 3: Find the number of pens for Sanjay
Substitute 4y for x in the first equation to have;

Hence, Sanjay has 8 pens