Let b be the number of branches that the shrub will have after m months, since the shrub has an initial amount of 12 branches and the shrub grows 4 new branches every month, then we can set the following equation:
Evaluating the above equation at m=7 we get:
Simplifying the above result we get that the shrub will have
7.2 hours a day. You get this answer by dividing 24 by 10 because that is 10% which is 2.4, multiply this by three which equals 30% and the answer is 7.2