Rule 1: 1. شَارَكَ، اِتَّفَقَ، وَافَقَ
شَارَكَ (imperfect يُشَارِكُ) to go into partnership with, to share with takes a direct object for the partner and فِي for the business: شَارَكَ النَّجَّارُ التَّاجِرَ فِي الْعَمَلِ. اِتَّفَقَ (يَتَّفِقُ) to agree is used with عَلَى for what is agreed and مَعَ for the other party; it begins with a joining hamza, so after وَ it is read wa-ttafaqa. وَافَقَ (يُوَافِقُ) to consent, to agree to takes عَلَى. Note the dual endings when the subject is two partners: اِتَّفَقَا, عَمِلَا.
شَارَكَ سَالِمٌ تَاجِرًا فِي السُّوقِ.
shāraka sālimun tājiran fi-s-sūqi
Salim went into partnership with a merchant in the market.
اِتَّفَقَ الشَّرِيكَانِ عَلَى شَرْطٍ.
ittafaqa-sh-sharīkāni ʿalā sharṭin
The two partners agreed on a condition.
اِتَّفَقَا عَلَى قِسْمَةِ الرِّبْحِ.
ittafaqā ʿalā qismati-r-ribḥi
The two of them agreed on the division of the profit.
Dual perfect.
وَافَقَ التَّاجِرُ عَلَى الشَّرْطِ الْجَدِيدِ.
wāfaqa-t-tājiru ʿala-sh-sharṭi-l-jadīdi
The merchant agreed to the new condition.
هَلْ تُوَافِقُ عَلَى هٰذَا؟
hal tuwāfiqu ʿalā hādhā
Do you agree to this?