when multiplying two binomials together we use the F.O.I.L. method:
First
Outer
Inner
Last
(7-3i)(2-i)
First: 7 2 ..... Outter: 7 -i .... Inner: -3i 2 ...... Last: -3i -i
First: 14 ...... Outter= -7i ..... Inner: -6i .... Last: 3i^2
putting this together we get 14-7i-6i+2i^2
We combine like terms and end up with 2i^2-13i+14