Find the simple interest rate if $1,200 earns $81 interest in 9 months.

Please help with a step by step thank youuu!!!

the simple interest rate is 9%

Step-by-step explanation:

The formula for determining simple interest is expressed as

I = PRT/100

Where

I represents interest paid on the amount invested.

P represents the principal or amount invested.

R represents interest rate

T represents the duration of the investment in years.

From the information given,

P = $1200

T = 9 months = 9/12 = 0.75 year

I = $81

Therefore,

81 = (1200 × R × 0.75)/100

81 = 900R/100 = 9R

R = 81/9

R = 9%

option c) graph of line going through 1, 4 and 3, 10

step-by-step explanation:

let y equal to margo's coin collection

let x equal to number of years

at the begining x=0, y=1 → point=(x,y)→point=(0,1)

she adds 3 coins per year, then y=1+3x

at x=1, y=1+3(1)=1+3→y=4→point=(x,y)→point=(1,4)

at x=3, y=1+3(3)=1+9→y=10→point=(x,y)→point=(3,10)

the graph of line going through (1, 4) and (3, 10), then the option c is the correct.