Matthew is 7 years older then twice the age of his sister. if matthew is 13, how old is his sister? (not subtraction, its much more)

S = sisters ages

M =2S +7

M=13

13 = 2S+7

subtract 7 from each side

6 = 2S

divide by 2

3=S

sisters age is 3

b) 1/3 * 1/5

step-by-step explanation:

each smallest part is 1/15 since the written one is 1/5 and it's divided by 3 equal parts. (1/5 )/3 = 1/15 = 1/3 * 1/5