Your problem is giving you d in terms of t, meaning that it is asking if we replace t with 11, what would d be?
When a number is right in front of a variable, they are being multiplied
So if t is 11, and the problem shows 11t, we replace the t with 11 and put parentheses around it
d = -20 + 11t
d = -20 + 11(11)
d = -20 + 121
d = 101
And there you have it! Your final answer is d = 101!
Practice pre-algebra and plugging in numbers into equations! Having mastery over the basic math functions and rules, as well as Order Of Operations, makes all of this so much easier!
I recommend that you watch Khan Academy videos and practice problems on there! It is a great resource! What you are learning would most likely fall under pre-algebra!
