MHB Make x the subject of 2x/5-3b/4=x+5

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To rearrange the equation 2x/5 - 3b/4 = x + 5 and make x the subject, the fractions can be eliminated by multiplying both sides by 20, the least common multiple of the denominators. This results in the equation 8x - 15b = 20x + 100. Rearranging gives -15b - 100 = 12x, which simplifies to x = -(15b + 100)/12. The discussion highlights the importance of properly handling terms when moving them across the equation, as mistakes can lead to incorrect conclusions about the value of x. Understanding these steps is crucial for solving similar algebraic equations effectively.
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hi to all
looking for some help to rearrange a formula to make x the subject
2x/5-3b/4=x+5

i moved +5 to the left and it became -5
i thought the negative 5 would cancel the denominator 5

this is what i thought i could do

2x-3b/4=x

-2x -2x

-3b/4 =-x
multiply both sides by -1 and the result i thought should be

3b/4=x
thanks in adv
 
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$$\frac{2x}{5} - \frac{3b}{4}=x+5$$

To clear fractions, multiply both sides of the equation by $20$, the $\text{lcm}$ of $5$ and $4$:

$$8x-15b=20x+100$$

Rearrange so $x$ is on its own on one side of the equation:

$$-15b-100=20x-8x$$

Simplify:

$$-15b-100=12x$$

Divide through by $12$:

$$x=-\frac{15b+100}{12}$$
 
Thanks for that all i can do is learn
Cheers
 
blackfriars said:
i moved +5 to the left and it became -5
i thought the negative 5 would cancel the denominator 5
Make up a simple case:
x/5 = 5 : evident that x = 25, right?
Now, move the 5 as you did:
x/5 - 5 = 0 : ok?
Cancel the denominator with the -5:
x = 0
BUT x = 25 : convinced?
 
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