Question on an SAT question

Question

Assume that when adults with smartphones are randomly​ selected, 51 ​% use them in meetings or classes. If 15 adult smartphone users are randomly​ selected, find the probability that fewer than 4 of them use their smartphones in meetings or classes. The probability is nothing.

I need help how to calculate it without the high tech calculator, just with ti-30x.

Answer 1

combination(15,0) * (.51)^0 *(1-.51)15 + combination(15,1) * (.51)^1 *(1-.51)14 + combination(15,2) * (.51)^2 *(1-.51)13 + combination(15,3) * (.51)^3 *(1-.51)12 = 0.0145