30 is equal to thrice y decreased by z
Thrice y means we multiply y by 3:
3y
Decreased by z means we subtract z from 3y
3y - z
The phrase is means an equal to, so we set up an equation where 3y - z is equal to 30
3y - z = 30
Thrice y means we multiply y by 3:
3y
Decreased by z means we subtract z from 3y
3y - z
The phrase is means an equal to, so we set up an equation where 3y - z is equal to 30
3y - z = 30