Question

Put the same number in each box to make the
calculation correct.
140 + 10 - ___ = _____ - 30

Answer 1

Answer:

The number would be 90

Step-by-step explanation:

140 + 10 - 90 = 60

90 - 30 = 60

60 = 60

Answer 2

Answer: 90

Step-by-step explanation:

Let's use x as a placeholder to the number we are trying to find

$140+10-x=x-30$

Now we need to isolate x

Step 1) Simplify both sides

$140+10-x=x-30\\150-x=x-30$

Step 2) Add 30 to both sides

$150-x+30=x-30+30\\180-x=x$

Step 3) Add x to both sides

$180-x+x=x+x\\180=2x$

Step 4) Divide both sides by 2

$\frac{180}{2}=\frac{2x}{2} \\90=x$

Step 5) Sub our value into the original equation and solve

$140+10-x=x-30\\140+10-90=90-30\\150-90=60\\60=60$