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.
You can divide the whole expression by -3:

Recalling that

Let's compare the middle term:

So, we want to complete

Which differs from
by 16. So, if we add 16 to both sides, we have

Answer:
2/8, 3/12 and 4/16
Step-by-step explaination:
All these fractions are equivalent to 1/4 as the numerator is a multiple of 1, the denominator is a multiple of 4, and the numerators are all a quarter of their respective denominators.