Answer:
Hiroshi's error was not having changed the sign of the number 37 by removing the parentheses and placing -37 instead of +37.
Step-by-step explanation:
we have
Hiroshi's work
Remember that
a negative number is just a positive number multiplied by -1
and (-1)(-1)=+1
so
Correct work
therefore
Hiroshi's error was not having changed the sign of the number 37 by removing the parentheses and placing -37 instead of +37.