let

x = the number of susan's sales

y = the number fo yvess sales

susans sales last week were 177 less than four times yvess sales

x = 4y - 177

together their sales amounted to 1528

x + y = 1528

by solving the system of equations

x = 4y - 177

x + y = 1528

we find

x = 1187 sales

y = 341 sales

susan had 1187 sales while yvess had 341 sales.