Well theoretically speaking you could but that would take a long time and 15 and 30 have a common factor of 5 and 15. So I think for this one you can't since there are two common factors.
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Answer:
.
Step-by-step explanation:
(3x+1)+(2x+4)=90
3x+1+2x+4=90
5x+5=90
5x=85
x=17