The temperature Inside the lab refrigerator is at most 45 °F.
Use t to represent the temperature (in °F) of the refrigerator.
Remember that
At most is the same that "less than or equal to"
so
To get the 10% discount, a shopper must spend no less than $400.
Used to represent the spending (in dollars) of a shopper who gets the discount.
Let
x ------> the spending (in dollars) of a shopper who gets the discount.
no less ------> "greater than or equal to"
so