For this case we must solve the following equations:
[tex]5x + 7 = 3x + 21[/tex]
We subtract 3x on both sides of the equation:
[tex]5x-3x + 7 = 21[/tex]
We subtract 7 on both sides of the equation:
[tex]5x-3x + 21-72x = 14[/tex]
We divide between 2 on both sides of the equation:
[tex]x = \frac {14} {2}\\x = 7[/tex]
The second equation is:
[tex]3x-2 (5-x) = - 3 (x-10) + 3x[/tex]
We apply distributive property to the terms of parentheses:
[tex]3x-10 + 2x = -3x + 30 + 3x[/tex]
We add common terms:
[tex]5x-10 = 30[/tex]
We add 10 to both sides of the equation:
[tex]5x = 30 + 10\\5x = 40[/tex]
We divide between 5 on both sides of the equation:
[tex]x = \frac {40} {5}\\x = 8[/tex]
Third equation:
[tex]5 (x + 1) = 3 (2x + 3) +5[/tex]
We apply distributive property to the terms within parentheses:
[tex]5x + 5 = 6x + 9 + 5[/tex]
We add similar terms:
[tex]5x + 5 = 6x + 14[/tex]
We subtract 6x on both sides of the equation:
[tex]5x-6x + 5 = 14[/tex]
We subtract 5 on both sides of the equation:
[tex]-x = 14-5\\-x = 9\\x = -9[/tex]
Answer:
[tex]x = 7\\x = 8\\x = -9[/tex]