Answer:
There area 14 one cent stamps
Step-by-step explanation:
Let
x -----> the number of 1 cent stamps
y -----> the number of 8 cent stamps
z -----> the number of 12 cent stamps
we know that
0.01x+0.08y+0.12z=1.78 -------> equation A
x=y+4 ------> y=x-4 -----> equation B
x=2z -----> z=0.5x ------> equation C
substitute equation B and equation C in equation A and solve for x
0.01x+0.08(x-4)+0.12(0.5x)=1.78
0.01x+0.08x-0.32+0.06x=1.78
0.15x=1.78 +0.32
0.15x=2.10
x=14
therefore
There area 14 one cent stamps
What the maning of that ?
Ok. Something times 90 = 7200.
Let something = x
90x = 7200
Divide both sides by 90.
90x/90 = 7200/90
x = 80
The other factor is 80.
40s=360+30a
40s+30a=$3960
40s=360+30a
40s/40=360+30a/40
s = 9+3/4a
40(9+3/4a) +30a=$3960
360+30a+30a=$3960
360+60a=$3960
360-360+60a=$3960
60a=$3960
60a/60 = $3960/60
a= $60
The algebra book is $60
