This question uses expanding opcode technique.
Suppose we are provided with $x$ 2-address instructions, $y$ 1 address instructions and $z$ 0 address instructions
Then the formula is
Total 2-address instructions possible = $2^6$
$x< 2^{6}$
After utilizing x instructions, No of 1 address instructions remaining are
$(2^{6}-x)*2^{5}$
But we know we have $y$ 1 address instructions
So total 0 address instructions are
$((2^{6}-x)*2^{5})-y)*2^{5}$