Lesson 11.4: Solve the linear system model by multiplying first. (2 points)

The drama club had a car wash as a fundraiser where they washed a total of 41 vehicles. Members washed [tex]\( x \)[/tex] cars at [tex]\( \$ 5 \)[/tex] each and [tex]\( y \)[/tex] trucks at [tex]\( \$ 8 \)[/tex] each, and made a total of [tex]\( \$ 250 \)[/tex].

The system of equations
[tex]\[ \left\{ \begin{array}{l}
x + y = 41 \\
5x + 8y = 250
\end{array} \right. \][/tex]
can be used to represent this situation.

Find the number of each type of vehicle they washed.



Answer :

Certainly! Let's solve the system of linear equations given by the problem to find the number of cars [tex]\( x \)[/tex] and trucks [tex]\( y \)[/tex] that the drama club washed.

We have the following system of equations:
1. [tex]\( x + y = 41 \)[/tex]
2. [tex]\( 5x + 8y = 250 \)[/tex]

We can solve this system step-by-step.

### Step 1: Express one variable in terms of the other using the first equation

From the first equation:
[tex]\[ x + y = 41 \][/tex]

We can solve for [tex]\( y \)[/tex] in terms of [tex]\( x \)[/tex]:
[tex]\[ y = 41 - x \][/tex]

### Step 2: Substitute this expression into the second equation

Now we substitute [tex]\( y = 41 - x \)[/tex] into the second equation [tex]\( 5x + 8y = 250 \)[/tex]:
[tex]\[ 5x + 8(41 - x) = 250 \][/tex]

### Step 3: Simplify and solve for [tex]\( x \)[/tex]

First, distribute the 8:
[tex]\[ 5x + 8 \cdot 41 - 8x = 250 \][/tex]

This simplifies to:
[tex]\[ 5x + 328 - 8x = 250 \][/tex]

Combine like terms:
[tex]\[ -3x + 328 = 250 \][/tex]

Subtract 328 from both sides to isolate terms involving [tex]\( x \)[/tex]:
[tex]\[ -3x = 250 - 328 \][/tex]
[tex]\[ -3x = -78 \][/tex]

Divide both sides by -3:
[tex]\[ x = \frac{-78}{-3} \][/tex]
[tex]\[ x = 26 \][/tex]

So, the number of cars [tex]\( x \)[/tex] washed is 26.

### Step 4: Find [tex]\( y \)[/tex] using the value of [tex]\( x \)[/tex]

Substitute [tex]\( x = 26 \)[/tex] back into the equation [tex]\( y = 41 - x \)[/tex]:
[tex]\[ y = 41 - 26 \][/tex]
[tex]\[ y = 15 \][/tex]

So, the number of trucks [tex]\( y \)[/tex] washed is 15.

### Conclusion

The drama club washed:
- [tex]\( 26 \)[/tex] cars, and
- [tex]\( 15 \)[/tex] trucks.

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