for the first problem you would add 1 to both sides, and you would get 5x=15, then you would divide both sides by by 5 to get x by itself. 5x/5=x and 15/5=3, so x=3. you can also plug it in. 5(3)-1=14
for the second one you wpuld subtract 15 from both sides, and you would get 3x=30. divide both sides by 3 which is x=10. plug it in, 15+3(10)=45.