book Maths Puzzle Numerical Ability

ok i have done 21 of these and here are the ones i cant get...

Use log9^7=0.8856 and log9^4=0.6309 to evaluate each expression

log9^28
log9^49
log9^144
log9^15.75

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book Other Question

Solution A is 8% acid and Solution B is 4% acid. If a technician wants to mix them to make 150 liters of Solution C which is 6% acid, how many liters of each should be mixed together?
thanks for the help! there were 429 people at a play. admission was $1 for adults and $0.75 for children. the receits were $372.50. how many adults and how many children attended the play?