Can someone please help me to solve 3/4 problems pls i will mark you the brainly pls I need help

Answer:
3. x = 11.6
4. f = 2 g = 2
Step-by-step explanation:
3) (3x - 7) + (4x + 6) = 90 --> x = 11.6
4) 3f + 1 = 5f - 15 ---> f = 2
6g - 5 = 3f + 1
6g = 3(2) + 6 ---> g = 2