hi just need a quick hand not the answer please

the question is

z = (2-i)

w=(5+3i)

so work out

a)zw

b)z/w

both of which i can do with no problem but the last bit is

c) |w|

can some one please tell me what the 2 straight lines mean on each side of the w thank you 4 ur time and any help

also im a bit stuck with this simultaneous equation i have never done them with fractions in i think it is easy but i might just be looking at it in the wrong way

4/x+1/y=5/3

1/x-3/y=3/2

should i be trying to get it on 1 line so times it by xy any help would be very greatfull thank you