Question

Please help me with numbers 4, 6, & 7

Answer 1

Problem 4:
$\rm \frac8{11}(n-10)=64$

multiply by 11,

8(n-10) = 64*11

divide by 8,

n-10 = 8*11

Add 10,

n = 88 + 10 = 98
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Problem 5:
-0.6(r+0.2)=1.8

Divide by -0.6,

r+0.2 = -3

subtract 0.2,

r = -3 - 0.2 = -3.2
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Problem 6:
$\rm \left(w-\frac49\right)\left(-\frac23\right)=-\frac45$

I hope this method isn't too confusing for you,
but I would multiply through by the LCM of the denominators to get rid of the fractions. LCM of 3, 9 and 5 is 45.

Multiply both sides by 45,

(45w - 20)(-30) = -36

Divide -30,

45w - 20 = 36/30

Add 20,

45w = 36/30 + 20

Divide 45 as a final step,

w = 21.2/45