Hello there!
ax + bx = 13
We want to start by factorizing out the variable x
x(a + b) = 13
Then divide both sides by a+b
x( a + b)/a + b = 13/a+b
x = [tex]\frac{13}{a+b\\}[/tex]
2)
ax + 5 = cx
Should start by adding -cx on both sides
ax + 5 - cx = cx - cx
ax + 5 - cx = 0
ax - cx = 0 - 5
ax - cx = -5
Then again, we need to factor out x because there's two of them
x( a - c) = -5
Then divide both sides by a-c
x(a - c)/ a - c = -5/a - c
x = [tex]\frac{-5}{a-c}[/tex]
3)
ax + b = dx - 1
Start by adding -dx on both sides
ax + b - dx = dx - 1 - dx
ax - dx + b = -1
ax - dx = -1 - b
Here we go again, factor out x
x( a - d) = -b - 1
x = [tex]\frac{-b-1}{a-d}[/tex]
I hope these answers help. As always, it is my pleasure to help students like you. Let me know if you have additional questions.