Question

three more than 8 times a number is -29.find the number

Answer 1

lets call the unknown number x
1. "3 more than" means "3+"
2. "8 times a number" means 8x

so your word equation can be written down as:
3+8x=-29

now you just need to solve this to find "x".

Answer 2

3+8x=-29
8x=-32
x=-4