As the question is stated 1.5 does not equal 90. But if some units are added, then this could be true, like for example: 1.5 hours = 90 minutes, is a true equality.
6 x 15 = 90
90 minus 75 =15 therefore 15 + 75 = 90
15 times 90 equals 1350.
105
15 + 80/90 = 143/9 = 15.888
81
90 divided by 6 equals 15.
sigh, 18...
6 goes into 90 exactly 15 times.
6
0.45
15 times 6 = 90