Understanding the Equation: Solving 90 + 2ab = 54 Step-by-Step

In algebra, solving equations step-by-step is essential for clarity and accuracy. One such common problem involves simplifying linear equations with variablesโ€”like solving 90 + 2ab = 54 to find the product ab = 27. This article breaks down the process clearly, helping students, tutors, and math learners master basic algebraic manipulation.


Understanding the Context

What Is the Equation?

We begin with the equation:
90 + 2ab = 54

Our goal is to isolate ab and find its value. This type of equation often appears in math education when teaching simplification and solving for variablesโ€”a crucial foundation for more advanced algebra.


Key Insights

Step-by-Step Solution

Step 1: Subtract 90 from both sides
To eliminate the constant term on the left, subtract 90 from both sides:

90 + 2ab โ€“ 90 = 54 โ€“ 90  
2ab = โ€“36
```

**Step 2: Divide both sides by 2**  
Next, divide both sides by 2 to isolate `ab`:  

2ab รท 2 = โ€“36 รท 2
ab = โ€“18

Wait! At this point, we see ab = โ€“18, but this doesnโ€™t match the expected value (ab = 27). This discrepancy indicates a potential typo or misstatement in the original equation.


Final Thoughts

Fixing the Equation for a Correct Result: ab = 27

Letโ€™s reverse-engineer the problem to achieve ab = 27. Starting again from the original equation:
90 + 2ab = 54, but if we want ab = 27, rearrange the equation correctly:

90 + 2(27) = ?
2ab = 2 ร— 27 = 54
90 + 54 = 144 โ‰  54
``

Clearly,90 + 54 = 144โ€”so the original equation90 + 2ab = 54cannot yieldab = 27.


Corrected Equation for ab = 27

To satisfy the conditionab = 27, the original equation must be adjusted. Suppose instead:
What if 90 + 2ab = 90 + 54?
Then:
90 + 2ab = 144Subtract 90:2ab = 54Divide by 2:ab = 27โœ…


Summary: Corrected Workflow

  1. Start with90 + 2ab = 1442. Subtract 90:2ab = 543. Divide by 2:ab = 27

This confirms the logic and shows how precise algebraic manipulation leads to accurate results.