To solve for x, we follow these steps:

Start by adding 3/7 to both sides of the equation:
4x = 31 + 3/7

Convert the fraction 3/7 to a decimal:
3/7 = 0.428571 (approximately)

Add 31 and 0.428571:
31 + 0.428571 = 31.428571 (approximately)

Divide both sides by 4 to isolate x:
x = 31.428571 / 4
x = 7.857142 (approximately)

Therefore, x is approximately 7.857142.