Question 149526
Alright in this one you have a couple steps...

First we're gonna start with the longer equation and simplify it.

You have:
10t+u+9=10u+t
first you're going to get all your t's on one side:
(-t)10t+u+9=10u(-t)+t
9t+u+9=10u

Now you're gonna get all your u's on one side:
9t(-u)+u+9=10u(-u)
so you end up with...
9t+9=9u

Now you're gonna factor out a nine from the whole equation...

9(t+1)=9u

Now, you can divide both sides by nine, so you're left with a clean equation.

t+1=u

Ok... you're gonna add the other equation in now... Don't be scared lol.

We're going to isolate the t variable in the first equation so...

t+u=7
t=-u+7

now we'll subsitute this equation for t in the other equation like this:

t+1=u
(-u+7)+1=u
Solve
-u+8=u
8=2u
u=4

wualla!! you got it!