Question

find the missing number to make the equation true.
$7 + 8 + \underline{\quad} = 30 - 5$
first, you can find the value of the side with no missing number.
$30 - 5 = 25$
the two sides are equal. so,
$7 + 8 + \underline{\quad} = 25$
$15 + \underline{10} = 25$
$7 + 8 + \underline{10} = 30 - 5$
the missing number is 10.
set h
thinking habits
reasoning
how are the numbers in the problem related?

Explanation:

Step1: Calculate right-hand side

$30 - 5 = 25$

Step2: Sum known left-hand terms

$7 + 8 = 15$

Step3: Solve for missing number

Let $x$ = missing number.
$15 + x = 25$
$x = 25 - 15 = 10$

(for Thinking Habits):
The numbers are related by the equality of both sides of the equation. The right-hand side simplifies to a fixed value, and the left-hand side's known values are summed to find the missing number that makes both sides equal, maintaining the balance of the equation.

Answer:

10