I have several questions, I'd appreciate if anyone would give tips/solutions/corrections!

1) solve : 3^{2x}-5(3^{x})=-6

answer: 1 & 0.631

I tried to divide out the "-5", so the right side was "6/5". Then I converted it to log forms and solved for x by dividing them, however, this didn't get me the right value.

2) The half-life of stronium-90 is 25 years. For 100 mg sample, estimate the rate of decay after 15 years.

answer: -1.83 mg/yr

I know that the formula is M=M_{o}(0.5)^{t/hl }and I subbed in the values.

M = (100)(0.5)^{15/25 }M = 65.98 mg

Now I'm not sure how to find the rate of decay? Any suggestions?

3) The population of a small town increases by 3.5% per year. If the population in 1995 was 2300 people, estimate the rate of growth of the population in 2005.

answer: approx. 112 people/year

I subbed in the values into y = c(1+i)^{x}and the population in 2005 will be about 3244 people. Again, not sure how to find the rate of growth.

4) Stronium-90 loses 2.5% of its mass each year. What is its half life? Estimate the rate at which he mass is decreasing after 5 years.

answer one: 27.38 years

answer two: 2.23%/year

Now I'm not sure how to solve this one because I feel like its missing some values and I don't know how to work with the formulas then.

Thank you in advance!