If filing joint married with both spouses born before 1959, and one 14 year old child dependent; how many standard deductions can i claim ?

There are no personal exemptions.  There is only one standard deduction based on your filing status.

Standard deductions for 2023

Single - $13,850 add $1,850 if age 65 or older
Married Filing Separately - $13,850 add $1,500 if age 65 or older
Married Filing Jointly - $27,700 add $1,500 for each spouse age 65 or older
Head of Household - $20,800 add $1,850 if age 65 or older

The standard deduction of $27,700 plus $1,500 for each spouse age 65 or older will be found on line 12 of the Federal 1040 tax return.

Personal exemptions for dependents were removed from tax law under the Tax Cuts and Jobs Act of 2017.  Higher Child Tax Credits replaced the personal exemptions.

If you meet all of the eligibility factors, the maximum amount of the child tax credit is $2,000; for the 2023 tax return, the refundable amount is $1,600 depending on your income.  For 2023, you must have earned income (income from a job) of at least $2,500 to be eligible for the refund.

If your child is older than 16 at the end of 2023, you do not get the Child Tax Credit.  But you may still qualify for the non-refundable $500 credit for other dependents instead.