    Sentence    4: What nioderi math’coneept did ZhuShijie. do, work  similar to?    Séntence 2hé mathematician’ Zhu Shijfe. (1249-1314)  solved :   siaultanéous équation’s -with up to”four. unknowns}  uising a rectangular artay of coefficients, equivalent: to}  nigdern riatrices.