For this case we have the following equation:
[tex]\frac {2} {5} * (3r + 4) = 10[/tex]
We must clear the variable "r":
We multiply by[tex]\frac {2} {5} * (3r + 4) = 10[/tex] \ frac {5} {2} on both sides of the equation:
[tex]\frac {2} {5} * \frac {5} {2} (3r + 4) = 10 * \frac {5} {2}\\3r + 4 = \frac {50} {2}\\3r + 4 = 25[/tex]
We subtract 4 on both sides of the equation:
[tex]3r + 4-4 = 25-4\\3r = 21[/tex]
We divide between 3 on both sides of the equation:
[tex]\frac {3r} {3} = \frac {21} {3}\\r = 7[/tex]
Answer:
[tex]r = 7[/tex]
