18.5×59/5 - 11.8× 69 /4
= 18.5×11.8 - 11.8× 17.25
= 11.8×(18.5 - 17.25)
= 11.8× 1.25
= 1.25×(10+1+0.8)
= 12.5+1.25+1
= 14.75