$824= cost of washer & dryer
d= cost of dryer
w= d-76 cost of washer
d + w= $824
substitute w=d-76 in equation
d + (d-76)= 824
combine like terms
2d -76= 824
add 76 to both sides
2d= 900
divide both sides by 2
d= $450 cost of dryer
substitute dryer cost in washer equation
w= d-76
= 450-76
= $374 cost of washer
Check:
450+374= 824 total
824=824
Hope this helps!