Two dimensional parity check
Firstly the $t&lt;d$ condition, applies to either the row or the column codes on their own. So you know that a single error in each row or column can be detected since $d=2$.

Given 3 errors overall for the array, consider the decompositions of errors into distinct rows. Clearly 


$3=3$,
$3=2+1$, or
$3=1+1+1$


are the only possibilities.

In case 3 the column parity checks can correct these errors separately so we're done.

In case 2 the single error can be corrected on its row, and the remaining two errors on a single row, can be corrected  by the parity check in the corresponding column.

In case 1 all 3 errors are on one row, so by definition they are on 3 distinct columns and can be corrected by the parity check in the corresponding column.

So the array code can correct 3 errors.