(8a^2b^-5c^3)(-2ab^-3c^-2)=-16a^4

Multiply the terms:<br /><br />$-16a^3b^{-8}c = -16a^4$<br /><br />Divide both sides by $-16a^3$:<br /><br />$b^{-8}c = a$<br /><br />$c = ab^8$<br />