Hey there!
Let's call this "number" x. We want four times the sum of this number and 15 to equal at least 120.
Therefore, we want this number times four plus fifteen to be greater than or equal to 120. We have:
[tex] 4(x+15)\geq 120 [/tex]
Distribute:
[tex] 4x + 60 \geq 120 [/tex]
Subtract:
[tex] 4x\geq 60 [/tex]
Divide:
[tex] x\geq 15 [/tex]
Your answer is C.
Hope this helps!
