Call the number of pages he has read, R
Call the number of pages he hasn't read, 193 - R
So...we have that
R = 3 + (1/4)(193 - R) simplify
R = 3 + 193/4 - (1/4)R add (1/4)R to both sides
(5/4)R = 3 + 193/4 multiply through by 4
5R = 12 + 193
5R = 205 divide both sides by 5
R = 41 = pages he has read
So .... he hasn't read (193 - 41) = 152 pages
Proof :
(1/4) of the pages he hasn't read = 152/4 = 38 pages
And 3 more than this = 41 = pages he has read .....