Okay, the problem was that I had typo'd my notes -.- It should be 7+3 = 10 mod 11 which is much more logical.

My problem now is that I need to use the answer to "Find a number in /7 which gives 1 mod 7 when multiplied by 3" (the answe of which is 5)

to solve the equation "3n = 4 in /7" and don't know where to start.

Any ideas/insights?