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Row 0 has one number

Row 1 has two numbers

.

.

.

and so on

Therefore, row 42 must have 43 numbers.

The first number starts $\binom{n}{0}$with, the second number,  $\binom{n}{1}$ , and so on..

Thus, the answer is $\binom{42}{1}=\boxed{42}.$

Hope that helped!