Ineed to find the value of x. but the teacher never told us how to do this! can anyone ?

First of all, you need to know that a triangle always adds up to 1ip degrees. So, you have to create and equation that goes like this:
7x+11+90+25=180
You combine like-terms so in simplest form its:
7×+126=180
After this you follow the procedure to solving 2-step equations.
If you have any other questions, I'll be happy to help.

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