Solve the Equation: Finding the Value in 45 + △ = 50

Let's solve the problem step by step:

• Step 1: Start with the equation provided: $45 + \triangle = 50$.

• Step 2: To solve for $\triangle$, isolate it by subtracting 45 from both sides of the equation to maintain equality.

• This subtraction gives: $\triangle = 50 - 45$.

• Step 3: Perform the subtraction on the right-hand side: $50 - 45 = 5$.

Thus, the numerical value of the triangle ($\triangle$) is $5$.