He is incorrect because each number is in a different place and those different places are worth more or less than the other places
All you have to do is addition. 2+5+4=11. Or you can break it down and go 2+5=7 and then 7+4=11. Or 5+4=9 then 9+2=11. Or 4+2=6 then 6+5=11.
Jason would has 66 coins in his piggy bank because 31+26+29=86-20=66 Hope I could help!!
You would:
(4 * 2 - 4) + (3 - 2^2) + (2 * 2^3)
(8 - 4) + (3 - 4) + (16)
4 + -1 + 16 = 19
