4a + 6b = 10
2a - 4b = 12...multiply by -2
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4a + 6b = 10
-4a + 8b = - 24 (result of multiplying by -2)
------------------add
14b = - 14
b = -14/14
b = -1
2a - 4b = 12
2a - 4(-1) = 12
2a + 4 = 12
2a = 12 - 4
2a = 8
a = 8/2
a = 4
so 12a = 12(4) = 48 <==
20+0.15x = 35+0.10x
0.15x=15+0.10x
0.05x=15
x= 15/0.05
x= 300minutes
check:
300*.015 = 45+20=65
300*0.10 = 30 + 35 = 65
they equal
so number of minutes would be 300
Solution= x=5
Alernative form= 21 x - 105= 0<span />
