Tom, ted, tony and terry worked together on a job. the job paid $500. each boy was paid according to the amount of work he contributed to the job. ted and tony earned $280 together. ted and tom have $260 and ted and terry got $220. what percent of the job did each boy do?

For the answer to the question above,
Let d be Ted's portion; y be Tony's ; r be Terry's ; m be Tom''s
d+y+r+m=500
d+y+0+0=280
d+0+0+m=260
d+0+r+0=220

Using the Matrix function of a TI calculator to solve this system
of equations I get:
Ted = $130 ; so Ted did 130/500 = 26%
Tony= $150 ; so Tony did 150/500= 30%
Terry=$90 ; so Terry did 90/500= 18%
Tom = $130 ; so Tom did 130/500 = 26%